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Staying organized can be a challenge, especially when you have multiple commitments and tasks to manage. Fortunately, there are plenty of free online calendar schedulers available to help you stay on top of your schedule. With an online calendar scheduler, you can easily create and manage events, set reminders, and keep track of your daily activities. Here’s how you can get organized with a free online calendar scheduler.
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This text was generated using a large language model, and select text has been reviewed and moderated for purposes such as readability.
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How to use critical path method for complete beginners (with examples).
- What is critical path in project management?
- Understand the critical path method
- The critical path algorithm explained
- Float or slack in project management
- Dealing with contingencies and constraints
- What are the benefits of the critical path method?
- How to use the critical path method
Why must non-critical tasks be monitored?
Browse more blogs.
Originally published May 22, 2022. Updated with new information on September 21, 2022
How to use the critical path method for complete beginners
Critical path method: getti ng started in cpm & cpa.
Our CPM guide includes everything you need to get started in the Critical Path Method - with step-by-step examples, solutions, as well as schedules to help get your next project done faster and easier.
The Critical Path Method (CPM) is a simple but powerful technique for analyzing, planning, and scheduling large, complex projects. It is used to determine a project’s critical path—the longest sequence of tasks that must be finished for the entire project to be complete.
CPM, also known as Critical Path Analysis (CPA), identifies dependencies between tasks, and shows which tasks are critical to a project.
The Critical Path Method (CPM) is one of the most important concepts in project management, and certainly among the most enduring. But what is the Critical Path Method, exactly? This beginner-friendly guide will help you understand the Critical Path Method and apply it in your projects.
Early iterations of the Critical Path Method can be traced all the way back to the Manhattan Project in the early 1940s. Given the ambition, scale, and importance of this world-altering project, scientists - and the managers behind them - developed a number of techniques to make sure that the project delivered results on time. For a project management technique , the Critical Path Method has quite an illustrious history.
One of these techniques was to map out the most important tasks in any project and use that to estimate the project completion date.
Today, we know this technique as the Critical Path Method.
The Critical Path Method in project management is a cornerstone of project planning even to this day. How long a project takes often depends on the most important tasks that constitute it.
If you can map out these tasks and their duration, you can get a reasonable estimate of the project’s timeline and budget.
Don’t worry if all this sounds too much like jargon to you. In this beginner-friendly guide, I’ll teach you everything you should know about the Critical Path Method (CPM) and how it applies to project management.
Understand the Critical Path Method
Have you ever heard of the Theory of Constraints (TOC) ?
First described by Eliyahu Goldratt in his 1984 book, The Goal, this theory states that your ability to complete any activity hinges on a few critical resources or constraints.
For example, if you’re making a sandwich, you might have all the butter, ham, and cheese you need, but if you don’t have bread, you can’t make a sandwich.
The bread, in this case, would be the constraint your sandwich-making project depends on.
The Critical Path Method is similar to this theory, but broader in focus. According to this method, the success of any project depends on tasks along a critical path being completed on time.
Let’s look at this method in more detail.
What is the Critical Path Method and what is a Critical Task?
Every project, regardless of its size or budget, has some core tasks that are crucial to its completion. A task is defined as critical if delaying it will slow down the completion of the entire project.
Take something as simple as making an omelet.
If you had to create a short recipe for making an omelet, it would look something like this:
- Beat 2 eggs
- Heat a pan, add butter/oil when hot
- Pour in the beaten eggs and cook for 5 minutes
There are several other tasks you need to perform to make a good omelet. You have to season the eggs with salt and pepper. Maybe add some vegetables and some cheese. Perhaps you could flip it on the other side so the eggs are fully cooked through.
However, these activities are in addition to the three core steps in the recipe. Even if you don’t perform them, you’ll still have an omelet. Not a very good one, but an omelet nonetheless.
On the other hand, if you forget to beat the eggs, or heat the pan, or cook the eggs, you won’t have anything but a cold pan and two eggs.
This is to say, the three steps in the recipe describe the critical tasks necessary to make the omelet-making project a success.
And the sequence of these steps describes the critical path a new cook must take if he wants to make an omelet.
This is the Critical Path Method in a nutshell.
Critical Path Method Definition
The Critical Path Method is defined in the Project Management Body of Knowledge (PMBOK) as follows:
“The Critical Path Method is the sequence of scheduled activities that determines the duration of the project.”
These scheduled activities must be performed if the project is to be considered a success. Moreover, they must be completed in a specific order. If you’re building a house, you can’t construct the walls and then dig the foundation; you have to do it in a sequence.
The important bit to understand is that the CPM describes the longest sequence of tasks in the project.
That is, in any project, you’ll have multiple task sequences. The CPM would describe the sequence that takes the most time.
For example, if you’re building a house, you would have several task sequences as follows:
Each task takes a different amount of time and resources. It takes more time to build walls and lay the roof than to install faucets and fixtures.
If you had to figure out the project’s ‘Critical Path’, you would look at the sequence that takes the most amount of time, like this:
The total time taken to complete the sequence along this critical path would give you an idea of the project’s minimum duration.
You might undertake several task sequences simultaneously, but if there are any delays in the critical path sequence, your project will suffer delays as well.
The Critical Path Algorithm Explained
At its heart, the Critical Path Method is essentially an algorithm for decision-making. This algorithm takes a task's start time, its duration, and finish time to figure out which activities deserve the most attention (i.e. are "critical" for the project).
Let's consider an example to understand the critical path algorithm better.
Suppose you have a list of tasks as shown below. Columns C and D list the tasks that must be accomplished for the activity to begin, and the duration of the activity, respectively.
Since the project manager's goal is to complete the project as quickly as possible (without compromising on quality, of course), we'll try to find the earliest finish time for each activity.
To do this, organize all tasks into a flowchart and note their durations next to the task ID. The arrows indicate the sequence of activities. We'll mark the Earliest Start (ES) time to the left of the activity, and the Earliest Finish (EF) time to the right.:
Mark the Start Time (S) to the left and right of the first activity. Usually, this would be 0.
Now mark the Earliest Start (ES) time of each activity. This is given by the largest number to the right of the activity's immediate predecessor (i.e. its Earliest Finish time, or EF).
If the activity has two predecessors, the one with the later EF time would give you the ES of the activity.
The EF of an activity is given by its Earliest Start time (ES) and its duration (t), i.e. ES + t.
Thus, if an activity's ES is 20 and will last for 10 days, its EF will be 30.
Mark all these figures in the flowchart.
The longest path will be the “critical path”.
The final figure to the right of the last task in the sequence will give you the minimum time the project will take to finish.
Float or Slack in Project Management
A concept related to, and crucial for using the Critical Path Method is float or slack.
In project management, “float” defines the amount of time a task can be delayed without causing a delay in:
- Any subsequent, dependent tasks - called “free float”
- Any delay in the overall project - called “total float”
Any activity or task on the critical path has zero float. That is, you can’t delay it at all without causing a delay in the project or dependent tasks.
However, there are plenty of other activities in the project that can be delayed. The quantification of this delay is called the “float”.
For example, when you’re making an omelet, “Heating the pan” has zero float since it is on the critical path.
Seasoning the eggs, however, has a lot of float. You can add salt to the raw egg mixture, while the eggs are cooking, and even after they’ve cooked.
The importance of slack should not be understated. Calculating the float or slack of all activities in the project is crucial for better distribution of resources.
If an activity has a high float, you can divert its resources to a higher-priority task.
Generally speaking, high float activities will be lower down the priority list, while those on the critical path (aka ‘zero float’ activities) will get prime attention.
Dealing with Contingencies and Constraints
Rare is the project that goes according to plan. You will invariably have delays, scope changes, and client demands that will force you to hasten some activities and delay others.
The Critical Path Method includes several measures to deal with such contingencies:
1. Fast Tracking
Fast-tracking is the process of running multiple activities on the critical path in parallel in order to reduce overall project time.
Fast-tracking is only possible for activities that don't have "hard" dependencies, i.e. they don't depend completely on their predecessors to start.
For example, you need to dig the foundation before you can build the walls of a house. But while you're doing the digging, you can also buy bricks and mix the cement.
Thus, while "build walls" is dependent on "dig foundation", you can run "buy bricks" and "mix cement" in parallel to digging the foundation.
Obviously, fast-tracking requires additional resources. It can also impact overall quality since you're distributing resources to multiple tasks. Good resource management will come in particularly handy in situations where you need to run activities in parallel.
What if you need to rush an activity because of an early deadline?
In such a situation, you can allocate additional resources to the activity to bring it to completion faster.
This process is called 'crashing'.
Having a crash duration is useful in activities that:
- Benefit from having additional resources, i.e. follow a linear relationship between resources and time to completion.
- Can utilize resources from activities with high floats. Since there is significant "slack" in these activities, you can delay them without jeopardizing the project
Crashing is generally not recommended barring emergencies since it can impact activities on and outside the critical path. If you have to do it, however, divert resources from high-float tasks, not those on the critical path.
What Are the Benefits of the Critical Path Method?
In its September 1963 issue , Harvard Business Review had this to say about the Critical Path Method:
“Recently added to the growing assortment of quantitative tools for business decision making is the Critical Path Method—a powerful but basically simple technique for analyzing, planning, and scheduling large, complex projects.”
Since then, this method has established itself firmly in the theory and practice of project management. And for good reason - using the Critical Path Method offers countless benefits:
- Reduce delays: The Critical Path Method helps identify the most important sequence of tasks in a project. Managers can use this information to reduce delays by optimizing the work along the critical path, proactively preventing delays before they occur.
- Visualize dependencies: The CPM depends on listing all tasks associated with a project and their dependencies. The chart thus created can help you visualize all dependencies and prioritize tasks accordingly. Visualizing a Critical Path Method schedule can also simply give all stakeholders and resources a general roadmap of what to expect in any given CPM-driven process.
- Improve organization: In complex projects, the CPM helps break down deliverables into sequences, and sequences into tasks. This, along with the focus on visualizing dependencies, mapping constraints, and defining the critical path of tasks drastically improves project organization, ultimately making projects more manageable.
- Optimize efficiency: By mapping the critical path, project managers get a better idea of important tasks in the project. They can use this information to allocate resources more efficiently, adding/removing resources depending on the task's importance.
- Float calculation: Float, as we'll learn below, defines how much a task can be delayed without impacting the project schedule. This is an important part of the Critical Path Method. Calculating the float can help you distribute resources more effectively while being better prepared for any unforeseen issues that may arise at any point throughout the project.
If you’re a project manager - or aspiring to be one - there is another reason to understand the Critical Path Method: it is a core part of the PMP exam. You can’t really hope to be a certified project management professional without a deep understanding of this method.
In the next section, I’ll do a deep dive into CPM and show you how to use it in your projects.
How to Use the Critical Path Method
Project managers (PMs) use CPM to find the best way to schedule all the tasks in a project so that they can be completed as quickly and cheaply as possible. It helps them to prioritize tasks, anticipate bottlenecks, and identify task dependencies, resource constraints, and project risks .
The Critical Path Method can seem overly complicated until you actually put it to use. If you have a good understanding of core project management concepts such as the Work Breakdown Structure (WBS), you’ll find that CPM is delightfully simple.
I’ll walk you through a step-by-step process for using the Critical Path Method below.
A Step-by-Step Process for Using Critical Path Method
Recall our article on work breakdown structures (WBS)?
This WBS is the first ingredient in using the Critical Path Method. If you don’t understand the role of the WBS or how to create one, I encourage you to read our beginner-friendly article first.
Once you have a WBS, jump straight to the first step.
Step #1: Identify activities based on WBS
If you know your WBS, you would know that it describes deliverables, not activities. This is why all its components are described using nouns or adjectives, not verbs.
The CPM, however, focuses on activities described using verbs.
The first step of the CPM process, therefore, is to list all the activities required to create deliverables at each level of the WBS.
For example, if you’re making a sandwich, you might have the following activities associated with it:
This list of activities will form the foundation of the CPM, so make sure it is thorough.
Step #2: Identify all dependencies
Any project has two types of tasks:
- Tasks that depend on other tasks for their completion, i.e. dependent tasks
- Tasks that are independent of others and can be done in parallel to others, i.e. concurrent tasks
For example, if you’re making a sandwich, you can buy bread, vegetables, cheese, and chicken for it simultaneously. You can also chop vegetables while the chicken is cooking. Thus, these would be concurrent tasks.
However, buying bread and toasting bread are dependent tasks. You can’t toast bread if you don’t buy it, after a ll.
The next step in the CPM process is to establish which of the tasks are dependent and which are concurrent.
Go through your list of activities and identify which tasks each depends on, and in what order, like this:
A list of dependent tasks is called an activity sequence. You’ll use these sequences to figure out the critical path.
Step #3: Create a network diagram
Once you’ve identified all tasks and their dependencies, it’s time to create a network diagram, also known as a critical path analysis chart.
This chart visualizes separate activity sequences and enables you to map dependencies easily. To create it, make a list of all activity sequences. Create separate boxes for each task in the sequence.
Next, use arrows to identify dependencies between tasks in each sequence, like this:
This network diagram will form the basis of the final critical path.
Step #4: Estimate the duration of each activity
Recall that the critical path method describes the longest sequence of activities necessary to deliver the project successfully.
Thus, to figure out the critical path, we first need to estimate the duration of each activity. The activity sequence that takes the longest time would then be our critical path.
There are several tactics you can adopt to estimate the duration of an activity:
- Guesswork based on experience and knowledge
- Estimate based on past project data
- Estimate based on industry benchmarks
- Estimates based on extrapolated data
For example, if you know that it takes you 10 minutes to paint a 2’ x 2’ board (4 sq ft), you can estimate that it will take you 250 minutes to paint a 10’ x 10’ wall (100 sq ft).
However, even the best estimates can be inaccurate. Some tasks might be delayed because of unproductivity, delayed dependent tasks, or errors. Others might be completed earlier than expected because of an efficient worker.
To account for such contingencies, it is common to use three estimates for each activity:
- Best-case scenario, i.e. shortest duration (A)
- Normal scenario, i.e. expected duration (B)
- Worst-case scenario, i.e. longest duration (C)
The average of these three cases would give you a reasonable estimate of each activity’s duration.
Activity Duration = (A + B + C) / 3
If you’re dealing with activities you’ve performed several times in the past, you’ll likely have a better idea of its duration. In such a case, you can use a weighted average, giving additional preference to the “normal” scenario (B) according to your own confidence.
Weighted Activity Duration = (A + 2B + C)/4
List the duration (t) of each activity next to its name in the network diagram.
Step #5: Calculate the Critical Path
In your network diagram, write down the start and end time of each activity next to its box.
The first activity in the sequence would have a start time of ‘0’. Its end-time would be its duration.
The second activity’s start time would be the end time of the first activity. Its end-time would be the start time + the duration.
Do this for all the activities in every sequence, like this:
Now, look at the last activity in each sequence. The figure to its right would tell you the duration of the entire sequence.
The activity sequence with the longest duration would be your critical path.
Step #6 (Optional): Determine Floats
Float, as I mentioned earlier, is the amount of time an activity can be delayed without causing a delay in the project.
Calculating the float for all activities can help in resource planning. If an activity has a high float, you can divert resources from it to a higher priority task.
To determine float, follow this process:
- Find the second longest sequence of activities in the network diagram.
- Subtract its total duration from the duration of the critical path sequence
- The difference between the two durations will give you the float for each activity in the second sequence.
- If there are any common activities in both sequences, it will have a float of 0 since it is also on the critical path
You can do this for all other sequences to determine floats for every activity.
For example, in the diagram below, activities E, F, G, H, and I make up the critical path. Their total duration is 100 hours.
Activities B, C, D and E make up the second longest sequence with a total duration of 90 hours.
The difference between their total duration is 10 hours. However, since activities E is common and in the critical path, it would have zero float.
Hence, B, C, D - which are the non-common activities in the second sequence - would have a float of 10.
That’s it! You just used the Critical Path Method in a hypothetical project.
In the real world, you’ll rarely use network diagrams to chart the critical path. Instead, you’ll use Gantt charts to visualize tasks and their dependencies.
However, creating network diagrams and mapping critical paths manually can help you understand the concept better. It will also help you when you’re preparing for the PMP exam or actually managing projects.
Critical path method vs. Gantt chart
The Gantt Chart is a graphical tool that is used to display task dependencies and timing information. It can be used to track actual progress against planned progress and can help identify any potential problems with completing a project on time - and are often used in conjunction with Critical Path Method analysis to provide a more complete picture of the project. That said, there are some differences between the two.
If you need to track complex task dependencies and want a more detailed view of the project timeline then the Critical Path Method is the better choice. If you just need a simple way to track progress and don't need every detail, then Gantt Chart may be a preferred option.
In addition, the Critical Path Method should be used when you need to accurately predict the length of a project and when there are multiple dependencies between tasks. Gantt charts are best suited for projects where changes occur frequently and you need to be able to quickly adapt to those changes.
Non-critical tasks are not dependent upon the completion of other tasks so they can be executed before or after a certain project stage has been completed. However, as these tasks still need to be done for the project to be finished, forgetting one will push back the completion date of the whole project.
Critical Path Method vs. PERT
PERT is a project management technique that uses a probabilistic model to schedule and control uncertain activities, while CPM is a statistical technique that uses a deterministic model to schedule and control well-defined activities. The two techniques are quite different in their underlying assumptions and methodology.
PERT assumes that all tasks in a project are uncertain, and uses a probability distribution to calculate the expected completion time for each task. This allows for the estimation of the project's overall duration - given uncertainty in the individual tasks. CPM, on the other hand, assumes that all tasks are well-defined and can be scheduled with certainty. It uses a mathematical algorithm to calculate the shortest path through a network of tasks, known as the critical path. This allows for the determination of the earliest possible completion date for a project and its latest allowable completion date.
The PERT technique is the best choice when there is significant uncertainty surrounding the individual activities in a project. This uncertainty can be due to the nature of the activities themselves, or because the required resources for those activities are not yet known. The critical path method, on the other hand, is better suited for projects where all of the activities and their dependencies are well-defined and relatively stable.
Recent Updates and Developments in CPM
It's important to note that although CPM continues to play a major role in project management, new theories, and workflows seek to improve processes even further.
That said, the critical path method is still a popular way to schedule projects, despite some newer theories that have arisen in recent years. One such theory is the elasticity theory, which suggests that projects should be scheduled according to the flexibility of the deadlines. This takes into account the fact that unexpected delays can always occur and that it's better to have a project that's finished a little late than one that's rushed or never finished at all.
Other theories focus on using predictive analytics to calculate the best possible sequence of tasks in order to achieve the desired outcome. For example, some researchers are exploring how artificial intelligence can be used to help identify and optimize critical paths. This could help reduce the amount of time needed to complete a project and improve its overall efficiency.
Earned Value Management (EVM) is another project management technique that integrates cost, schedule, and scope information into a single performance measurement system. EVM can also be put into practice in conjunction with CPM, as EVM contractors often use it to assess project performance and determine whether a project is on schedule and on-budget.
Interestingly, most new updates or theoretical approaches draw inspiration from CPM itself.
Use Critical Path for Better Project Management
While there are no perfect solutions to project management, the critical path method is still one of the most popular ways to get the job done. Put plainly, CPM is used to compress and make schedules more efficient, quickly resolve resource shortages or resignations , and compile data for future use. Compressing a schedule means finding ways to complete the project in less time. This can be done by eliminating unnecessary tasks, shortening task durations, or overlapping tasks. Resolving resource shortages means making sure that all the resources needed to complete the project are available when needed and proactively knowing when additional resources may be needed. This can be done by reallocating resources, negotiating for more resources, or postponing tasks that can be done later. Compiling data for future use means gathering information about how the project was completed so it can be used as a guide for future projects.
As shown in the critical path method example above, CPM is a powerful project management tool. By having a foundational understanding of how CPM works and how it can be applied to your projects - rather than searching for a quick-fix Critical Path Method calculator - you can use it to improve your project management skills and increase your project's chances of success.
For CPM to work effectively, your schedule must be continually updated throughout the project to reflect any changes. Using project management software such as Workamajig will make it quicker and easier to plot and monitor your critical pathway and adjust your schedule when necessary.
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Critical Path Method (CPM) in Project Management
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What Is the Critical Path In Project Management?
What is the critical path method (cpm), cpm vs. pert, when should you use critical path analysis, what is the importance of cpm in project management, critical path diagram, critical path method (cpm) formula, critical path method example, critical path method steps.
- Benefits of Using CPM In Project Management
CPM Training Video
Cpm & project management software, must-have features of critical path software.
- How to Find the Critical Path with ProjectManager
In project management, the critical path is the longest sequence of tasks that must be completed to execute a project. The tasks on the critical path are called critical activities because if they’re delayed, the whole project completion will be delayed. To find the critical path, project managers use the critical path method (CPM).
The critical path method (CPM) is a project management technique that’s used by project managers to create an accurate project schedule . The CPM method, also known as critical path analysis (CPA), consists in using the CPM formula and a network diagram to visually represent the task sequences of a project. Once these task sequences or paths are defined, their duration is calculated to identify the critical path.
Related: 12 Free Project Scheduling Templates for Excel
Finding the critical path is very helpful for project managers because it allows them to:
- Accurately estimate the total project duration.
- Estimate the time that’s necessary to complete each project task.
- Identify critical activities which must be completed on time and require close supervision.
- Find out which project tasks can be delayed without affecting the project schedule by calculating slack for each task.
- Identify task dependencies, resource constraints and project risks.
- Prioritize tasks and create realistic project schedules.
Once done by hand, the critical path can now be calculated automatically with project scheduling software equipped with Gantt charts , which makes the CPM method much easier. ProjectManager is project management software that helps you quickly implement the critical path method. Build a project schedule on our award-winning Gantt chart, then simply filter for the critical path. When it’s time to execute, your team can collaborate with a task list, kanban board or calendar. And you can track everything with dashboards and reports to ensure you stay on track. Get started today absolutely free.
ProjectManager can calculate the critical path for you on our award-winning Gantt charts— learn more .
The critical path method was developed in the late 1950s by Morgan R. Walker and James E. Kelley. The origins of the critical path method are closely related to the Program Evaluation and Review Technique (PERT), a similar method that is commonly used in conjunction with CPM in project management .
The critical path method (CPM) and program evaluation and review technique (PERT) are both project scheduling techniques. But they aren’t interchangeable. We’ve been talking about CPM, but before we compare it to PERT let’s define the term.
PERT is used to get accurate time estimates for complicated projects. It uses an algorithm to calculate the estimated duration for unpredictable activities. It focuses on events and milestones on a PERT chart with nodes in the wireframe when developing projects.
However, while these are two different techniques, PERT and CPM can be used together for project planning and scheduling. The difference between them lies in that PERT is about time planning and time management, while CPM is about time and budgeting. PERT delivers a project quickly and CPM gets the project done on budget and on time.
Now that we know what’s the critical path of a project, we can learn about the critical path method (CPM), an important project management technique that’s based on this concept.
Critical path analysis is another way of referring to the critical path method. As noted, it’s used by industries with complex projects, such as aerospace, defense, construction and product development.
Therefore, critical path analysis is a crucial first step in developing a project schedule. It’s done early in the life cycle of a project, usually in the planning phase , but it’s not unheard of to have CPM as part of a project proposal before the project has been approved.
By understanding which are the critical tasks in a project you can focus on getting those done if time, resources and costs are an issue. Knowing this in advance of executing a project will help you deliver that project successfully.
Related: Free Project Plan Template
Projects are made up of tasks that have to adhere to a schedule in order to meet a timeline. It sounds simple, but without mapping the work, your project scope can quickly get out of hand and you’ll find your project off track.
Using the critical path method is important when managing a project because it identifies all the tasks needed to complete the project. It then determines the tasks that must be done on time, those that can be delayed if needed and how much float or slack you have.
When done properly, critical path analysis can help you:
- Identify task dependencies, resource constraints and project risks
- Accurately estimate the duration of each task
- Prioritize tasks based on their float or slack time, which helps with project scheduling and resource allocation
- Identify critical tasks that have no slack and ensure those are completed on time
- Monitor your project progress and measure schedule variance
- Use schedule compression techniques like crash duration or fast tracking
As you can see in this critical path diagram, project activities are represented by letters and the critical path is highlighted in green. Tasks F, G and H are non-critical activities with float or slack. We can also identify task dependencies between the critical path activities, and also between activities (A, F and G) or (A, H and E), which are parallel tasks.
Before we learn how to use the CPM formula, we need to understand some key CPM concepts.
- Earliest start time (ES): This is simply the earliest time that a task can be started in your project. You cannot determine this without first knowing if there are any task dependencies
- Latest start time (LS): This is the very last minute in which you can start a task before it threatens to delay your project timeline
- Earliest finish time (EF): The earliest an activity can be completed, based on its duration and its earliest start time
- Latest finish time (LF): The latest an activity can be completed, based on its duration and its latest start time
- Float: Also known as slack, float is a term that describes how long you can delay a task before it impacts its task sequence and the project schedule. The tasks on the critical path have zero float because they can’t be delayed
The critical path method formula has two parts; a forward pass and a backward pass.
Forward Pass in CPM
Use the CPM diagram and the estimated duration of each activity to determine their earliest start (ES) and earliest finish (EF). The ES of an activity is equal to the EF of its predecessor, and its EF is determined by the CPM formula EF = ES + t (t is the activity duration). The EF of the last activity identifies the expected time required to complete the entire project.
Backward Pass in CPM
Begins by assigning the last activity’s earliest finish as its latest finish. Then the CPM formula to find the LS is LS = LF – t (t is the activity duration). For the previous activities, the LF is the smallest of the start times for the activity that immediately follows.
Let’s take a look at a critical path example to better understand how the critical path method is used in project management. Although it’s high-level, it can help you visualize the meaning of a CPM schedule .
We’ll use this critical path diagram to explain the elements that make up the critical path analysis process. To keep things simple, we’ve already done the calculations for this example using the CPM formula.
The above critical path method example shows the critical path for getting a website online. All the tasks that are scheduled to build and launch the website are shown in the rectangular nodes.
Some of the tasks are being done at the same time as others. For example, the work on defining a target market is being done as the design is being done and the content for the site is being drafted.
However, not all these tasks are equally important. Some aren’t critical to getting the site live by the deadline. That’s where the critical path comes in. It has identified by the colored arrows all the tasks that must be done in order to complete the project plan on time.
Now that you know the key concepts of the critical path method, here’s how to calculate the critical path in 8 steps.
1. Collect Project Activities
Use a work breakdown structure to collect all the project activities that lead to the final deliverable.
2. Identify Task Dependencies
Determine which tasks are dependent on other tasks before they can begin. Use your judgment and your team members’ feedback. Failing to define task dependencies correctly makes the critical path method useless.
3. Create a Critical Path Diagram
A CPM diagram or network diagram , depicts the order of activities.
4. Estimate the Timeline
To use the critical path method, you’ll need to estimate the duration of each task. Use data from past projects and other sources of information such as subject matter experts.
5. Use the Critical Path Formula
The critical path uses an algorithm, also referred to as the CPM formula. That algorithm has two parts, the forward pass and the backward pass. The forward pass is determined by using the earliest start for each activity (ES) and the earliest finish (EF). The ES of an activity equals the EF of the one before it. The EF is calculated by EF = ES + t (the duration of an activity).
The backward pass assigns the last activity’s EF as its latest finish. Then use the CPM formula to find the LS, which is LF – t. For the activities before that, LF is the smallest of the start times for the next activity.
6. Identify the Critical Path
The activities with 0 float make up the critical path. All of these critical path activities are dependent tasks except for the first task in your CPM schedule. All project tasks with positive slack are parallel tasks to the critical path activities.
7. Revise During Execution
Continue to update the critical path diagram as you go through the project execution phase. These critical path analysis steps determine what tasks are critical and which can float, meaning they can be delayed without negatively impacting the project schedule. Now you have the information you need to plan the critical path schedule more accurately and have more of a guarantee you’ll meet your project deadline.
You also need to consider other changes or constraints that might change the project schedule. The more you can account for these unexpected events or risks, the more accurate your critical path schedule will be. If time is added to the project because of these constraints , that’s called a critical path drag, which is how much longer a project will take because of the task and constraint.
Benefits of Using CPM in Project Management
There are many reasons to use the critical path method. It’s a great project management tool to help you deliver your project on time and within budget , but we’ve already discussed that at length. Here are some other benefits of using CPM.
Critical Path Analysis Improves Team Communication
It fosters better communication within the project team . Everyone is involved in providing input and that brings the expertise of various project team members together for the better good of the project as a whole. This includes subcontractors, architects, electricians, construction managers, etc.
CPM Helps Prioritize Tasks
Naturally, having determined the critical path is going to help you prioritize your work. You know the tasks that must be done and that gives you wiggle room if there are issues with time or cost. You might not get every activity done, but you’ll get the ones finished that are critical to the project.
CPM & PERT Help Create Accurate Schedules
The critical path method will help you make a more accurate project schedule , especially when you use it in conjunction with PERT charts. You can estimate better and discover areas of risk and prepare to respond to them to avoid costly delays.
CPM & Gantt Charts Help Map Out Project Plans
Another benefit is the visual nature of CPM, especially when mapped on the timeline of a Gantt chart . Having a visual element to communicate the project schedule is always a plus. Not everyone absorbs information in the same way. Visual tools help teams better understand what’s expected of them and when it’s expected.
Do you still have questions about the critical path method? In this video, Jennifer Bridges PMP, explains how to find the critical path using a CPM diagram.
As stated, the critical path method (CPM) was first invented in the late 1950s. During those times, project scheduling software didn’t exist, and project managers had to calculate the critical path manually.
Fortunately, today there are many project management software alternatives that can help with the critical path process. Most of them use Gantt charts to represent CPM diagrams and calculate the critical path, but their feature sets vary greatly. One of the most commonly used project management software to identify the critical path is Microsoft Project . However, it has major drawbacks that make ProjectManager a better choice.
Here are some of the main features that you’ll need as a project manager to properly use the critical path method for your scheduling process.
Link Tasks and Avoid Bottlenecks
Tasks that are dependent on another need to be a part of your critical path calculation. There are four types: those that are start-start, start-stop, stop-start and stop-stop. By identifying these task dependencies , you can avoid bottlenecks later in the project.
Get a High-Level View of Your Progress
Dashboards are an essential feature for keeping track of critical path activities. They provide a window into the project’s performance and progress by collecting data and displaying it in graphs and charts that show various metrics, such as costs, tasks and more.
Make More Insightful Decisions
Keeping track of a project’s critical path as it’s executed is how you stay on track. But if the information you’re gathering is dated, then you’re always going to be playing catch up. With real-time data from a cloud-based CPM software, you’re always seeing the project as it currently is.
Know Your Project Variance
Schedules are always changing as the project is impacted by internal and external forces. To ensure you’re on target, you need to have project management software that’s collecting data and displaying project variance, so you can compare the actual progress against where you’ve planned to be.
Keep a Record of Your Plan
The critical path helps you plan the project, but once you’ve finalized the schedule, you need to set a baseline. This saves the schedule so you can compare it to your actual progress and know if you’re on time, behind or ahead. Any critical path software should have this feature.
See Deep Data on Performance
Reports serve two purposes. They take you deeper into the project and expose insightful data on project variance, timesheets and more, which helps you stay on track. Filtering the results and sharing the reports is a great communication tool for stakeholder presentations.
How to Find the Critical Path With ProjectManager
Figuring out the critical path by hand takes time, and it must be done throughout the project, which is why using project management software streamlines the process. ProjectManager is award-winning software that automates the critical path method process for you.
Our online Gantt chart filters for critical path, links dependent tasks and is integrated into a full project management software. Sign up for a free 30-day trial of our software and follow along to build a dynamic Gantt chart and automatically calculate your critical path in a few easy steps.
1. Start a Project With a Gantt Chart
Managing a project on Gantt charts allows you to both plan and schedule in one place. Add your tasks and their durations, and they’ll automatically appear on a project timeline, allowing you to see your whole project at once.
In the software, upload your tasks manually or upload a pre-existing spreadsheet. Add task descriptions, deadlines, priority, tabs and assign them to one or more team members. We also provide templates to help you get started.
2. Add Task Dependencies
In the software, connect your dependent tasks on the Gantt chart by dragging one onto the other. You’ll see a dotted line indicating that the tasks are linked, and you can then define the type of dependency it is.
3. Set the Project Baseline
Setting the baseline is possible when you’ve finished making your project schedule, complete with deadlines and costs. The baseline captures your data and uses it to compare against your actual progress.
On the Gantt chart, create your baseline for the project by adding the start date to the task and when it’s due to be completed. These planned start and end dates will be compared to your actual project data and show you whether you’re on target.
4. See the Critical Path
Easily find the critical path of your project by using our critical path filter. This helps you know what must be done to complete the project and shows if you’re experiencing any slippage.
5. See Your Overview With a Dashboard
Now that you’ve got your project planned out, viewing it from a dashboard is the best way to get a high-level view of your progress.
From the dashboard view, track if your project is proceeding as planned. Our dashboard monitors several project metrics, such as variance, tasks and more, automatically calculating your data to display it in easy-to-read charts and graphs.
6. Report on Progress
Reporting is crucial to pull data from your project and get and share insights into how it’s doing. Reports come in many varieties, which together provide a snapshot of the whole project’s performance.
Easily generate reports on the critical path, task progress, project status , costs and more in the software. We do the calculations for you, and you can filter the results to show just what you want to see. Our reporting feature is done automatically with one click.
ProjectManager is an online tool that gets real-time data to determine how accurate your planned schedule is to the actual one, so you can adjust immediately if necessary. See how it can help your project by taking this free 30-day trial.
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Critical Path Method Resources
- Critical Path Software
- Project Scheduling Software
- Gantt Chart Software
- Project Management Software
- Work Breakdown Structure (WBS) Template
- Gantt Chart Template
- Work Schedule Template
- Project Scope Template
- Top 10 Project Management Methodologies: An Overview
- 3 Free Tools for Making Network Diagrams
- Project Scheduling Guide
- The Ultimate Guide to Gantt Charts
- What Is a Work Breakdown Structure?
- PERT and CPM: Their Differences and How to Use Them Together
- The ABCs of the Critical Path Method – Harvard Business Review
- Understanding the Basics of CPM Calculations – PMI
- What Is the Critical Path in Project Management? – Elmhurst University
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Breaking down the critical path method (cpm) in project management.
July 31, 2023
In the world of complex projects, delivering on time is a must.
After all, missing deadlines is like wearing a neon sign that says unreliable to clients. To ensure success, adopting a realistic and meticulous planning approach is crucial.
You may not have superhuman capabilities, but you have the critical path method.
This powerful technique can help you supercharge your project management by precisely analyzing task dependencies and critical sequences! 💥
This article explains the critical path method, its benefits, use cases, and main elements. It’ll also provide step-by-step guidelines and suggest some helpful project management software to make implementing the critical path method easier, even for beginners.
Critical path medod vs. PERT
Benefits of using the critical path method in project management, when to use the critical path method, project activities, task dependencies, network critical path diagram, formulas and metrics, step 1: create a list of tasks, step 2: define task dependencies, step 3: visualize, step 4: estimate the task duration, step 5: identify the critical path, step 6: execute and revise, example of critical path analysis, what is the critical path method .
The critical path method is a series or sequence of must-do tasks determining the project’s overall timeline. We call such tasks critical activities, and they’re essential for the successful and timely execution of a project. ⏲️
The critical path method , also known as critical path analysis (CPA), is a technique project managers use to form accurate schedules across the entire project. They do so by identifying critical dependent tasks by calculating their duration using a specialized formula (or critical path algorithm).
They also often use Gantt charts or other diagrams to visualize and better understand the project timeline . Project managers use this to get a complete bird’s-eye view of the entire project and its dependent tasks to make better decisions.
The method was developed in the 1950s by Remington Rand’s James E. Kelley and DuPont’s Morgan R. Walker, who were looking to cut costs associated with inefficient scheduling. The pair also invented the Program Evaluation and Review Technique (PERT), a similar method often used alongside the critical path method.
CPM and PERT are both project management methodologies for planning and scheduling. Unlike CPM, which is a deterministic model, PERT is probabilistic, meaning it considers a range of possible durations for each task to provide a more flexible timeline estimation.
To delve deeper into their differences, refer to the table below:
Project managers will find many benefits to using the critical path method, including:
- Accurate estimation : Thanks to the critical path method, you can make predictions, set realistic expectations, and successfully plan the rest of the project
- Effective planning : Easily create a well-structured, realistic, and adaptable critical path project schedule and prevent major setbacks toward project completion
- Task prioritization : Critical path method helps you identify critical tasks that need to be at the top of your priority list and the most logical order of completing them
- Resource optimization : Once you know what must be done, by when, and in which order, you can effectively assign work and allocate other resources
- Improved communication : With a defined, visualized schedule, it’s easier to ensure everyone’s on the same page, which contributes to a smoother workflow
Critical path analysis should happen at the beginning of the project lifecycle . It’s typically performed in the planning stage before scheduling. In some cases, project managers carry this out even earlier and included it in the project proposal .
Industries that deal with complex projects , such as construction , engineering, and event planning, are the ones that benefit most from the critical path method. Besides projects involving many moving parts, the critical path method can also be helpful when it comes to time- or resource-constrained projects . 🚨
Key Components of the Critical Path Method
Before we start exploring CPM step-by-step, let’s learn its main concepts and their meaning. Think of the next section as your critical path method glossary ! 📖
In CPM, activities can be critical or non-critical . Critical activities are those you identify as important and include in the critical path. Non-critical project activities are all other tasks. They are less time-sensitive or essential, giving you more flexibility in scheduling.
Here’s a simplified example: If your project is to build a house, laying the foundation and installing the roof would be considered critical activities, while interior decoration would fall into the non-critical category. 🏠
Activities have their relationships, i.e., dependencies. What that means is that they have to happen in a specific order . For instance, some dependent tasks have to finish before others can start, or they have to start simultaneously.
To continue with our house-building example—you can’t start furnishing a room until you’ve finished the flooring and the wall paint has fully dried. 🛋️
The network critical path diagram is a flowchart for visualizing your project’s timeline and task dependencies . It consists of nodes, which are usually represented with rectangles or circles, and connectors, i.e., arrows.
Visualizing the structure of activities this way makes it easier to understand and identify the critical activities. A critical path diagram sometimes highlights areas in different colors to stand out from the non-critical task sequences.
You can also use Gantt charts and PERT charts to visualize your project timeline and critical paths, but more on that in the how-to section! 👀
The critical path method consists of a series of calculations to determine the duration of tasks and the critical path. The primary metrics are:
- Earliest start time (ES) : The earliest possible date you can start an activity considering the dependencies
- Earliest finish time (EF) : The earliest possible date you can complete an activity considering its ES and duration
- Latest start time (LS) : The last possible date you can start an activity before causing a significant project delay
- Latest finish time (LF) : The latest possible date you can complete a task based on its LF and duration
- Task duration (t) : The total amount of time it takes to complete an activity
The critical path formula has two parts, which we’ll explain below.
We use the forward pass to calculate the ES and EF .
The ES of the first activity on any path will always be 1 since it indicates the start, i.e., the first day of your project.
The ES of all other activities equals the earliest endpoint of the preceding activity plus 1:
ES = EF of preceding activity + 1
The EF equals the sum of ES and the duration of the activity minus 1:
EF = ES + t – 1
With the backward pass, we calculate the LS and LF .
The LF of the last activity on any path will always be the same, as it indicates the end, i.e., the last day of the project.
The LS of an activity equals the difference between LF and the duration of the task plus 1:
LS = LF – t + 1
The LF of an activity equals the LS of the succeeding activity minus 1:
LF = LS of succeeding activity – 1
The float or slack represents how long a non-critical task can be delayed without affecting the entire project timeline. Critical tasks don’t allow delays, so their float score is automatically 0.
There are two types of float:
- Total float : The amount of delay that doesn’t affect the project completion date (LS or LF – ES or EF)
- Free float : The amount of delay that doesn’t affect the start date of the succeeding task (ES of succeeding activity – EF of current activity)
How To Calculate the Critical Path in Project Management
Now that you’ve mastered all the elements of the critical path method, it’s time to put your knowledge to the test. In this section, we’ll show you how to calculate your project’s critical path in six steps. 🧮
Pro tip : If you opt for a project management tool like ClickUp , you can spare yourself from the manual and repetitive work. Instead of starting from scratch, use the pre-built ClickUp Critical Pathway Analysis Template .
With numerous task management features and intuitive Gantt charts, this tool makes CPM more accessible and streamlined! 🙌
The first thing you should do is determine the project scope . Collect all your activities in one place and define your goals, budget, and deadline.
ClickUp’s List View provides you with the perfect framework for that. It’s a spreadsheet in which you can list all the tasks, subtasks, and relevant information about them in custom fields, such as:
- Start and due dates
- Responsible department
- Accompanying documents
Feel free to add other custom fields to aid your project planning. You have over 20 field types at your disposal, including dropdown, checkbox, rating, and progress bar.
Besides listing tasks, you can also assign them, attach files, and lead discussions with your team in the comments.
Not a fan of spreadsheets and lists? Project managers can do everything in a Kanban-style ClickUp Board view as well to stay on top of the project schedule, uncover resource constraints, and see actual progress toward project completion.
Accurate identification of dependencies is crucial for successful time estimation and planning. Discuss with your team and use your previous experience to figure out the most logical order of tasks .
To define task relationships in ClickUp, right-click on a task and select the Dependencies option. You can choose between three types:
- Waiting on : Tasks that must be completed before the selected task
- Blocking : Tasks that can’t start before the selected task has been completed
- Related : Tasks that are related but not dependent on the selected task
Defining relationships is even easier in Gantt view. You only need to select the point on either side of the taskbar and drag it over to the corresponding point on the other task.
The best part is—this view allows you to automatically reschedule dependent tasks. To activate it, open the Show dropdown menu and toggle on the Reschedule Dependencies option.
Use a network diagram, work breakdown structure (WBS) , PERT chart , or any other visualization method to make the complex project task structure more comprehensible. Draw the flowchart and arrange tasks based on their chronological order and dependencies .
You can use pen and paper, a text editing or drawing program, or project management software like ClickUp.
ClickUp’s Whiteboard View lets you brainstorm and collaborate with your team on decisions. You can create good-looking WBS or PERT charts in no time. Use shapes and connectors to create the structure. Add additional elements like images and docs to make the diagram more informative.
As per usual, you can start with a template to save time. ClickUp has many ready-made frameworks for you to use, such as this universal ClickUp PERT Chart Template or the ClickUp Simple PERT Chart Template .
Although different in terms of structure, Gantt charts are also a convenient way to envision the sequence of tasks in a project and estimate their duration. In ClickUp, Gantt charts are interactive and adaptable. They enable you to draw the roadmap and schedule tasks simultaneously in only a few clicks.
The next step is to define the t for each task, i.e., how many days it will take to complete it. Estimate based on your experience, historical data, and industry standards . Consult others, particularly experts, to gain multiple perspectives and make the most accurate predictions.
Input the information in the designated fields in List View or update it directly in Gantt view by resizing the taskbars.
Using the formulas we shared earlier, calculate the ES, LS, EF, LF, and slack . Begin with the first task, which has a start time of 1, then define the EF and LF based on its duration. Repeat the same for all other tasks.
The longest sequence of critical activities (those that have 0 slack) is your critical path . You can also have multiple critical paths.
These calculations are much more manageable with ClickUp Gantt View . In your project Gantt chart , choose the Show option again, but this time, enable Critical Path and/or Slack Time .
The critical path will show up with a different color scheme, highlighting tasks with the blocking dependency in red. 🛑
With the Slack Time option enabled, a purple striped bar will appear alongside non-critical activities to depict the wiggle room they allow for. 🟣
Another way to discern critical from non-critical tasks is by adding priority tags and color codes. For instance, you can assign critical activities with a high-priority tag and non-critical activities with a low-priority tag, and the software will color them accordingly.
Finally, start bringing your project to life task-by-task. 🧱
As you go through tasks, you might realize some aren’t necessary or run into unexpected resource constraints. The delay caused by such events is called the critical path drag .
Monitor activities closely to ensure adherence to the schedule and catch any plan changes in time.
In ClickUp, you can ClickUp Goals and automatically track progress. Choose between task, numerical, monetary, and True/False targets, then manage them all in one place. By closely monitoring your targets and progress, you can ensure your project stays on the right path at all times. 🛣️
Remember our house-building example from earlier? Let’s expand on it! We’ll show you how to apply the critical path analysis to a real-life example.
We’ll be using the same ClickUp Critical Pathway Analysis Template.
Let’s start by listing all the tasks we need to take to build a house:
- Planning and design
- Site preparation
- Foundation construction
- Framing and structural work
We’ll also jot down the subtasks . For instance, in the planning and design stage, those would include:
- Hiring an architect
- Determining the house layout
- Acquiring all the permits
We’ll also define the project’s desired start and end date —May 18 to Mar 5.
Next, we’ll create a diagram in Whiteboard View. We’ll use the ClickUp PERT Chart Template to get a head start. Considering the dependencies and allotting larger shapes to tasks that require the longest time, we’ll create the flowchart to visualize the work ahead.
Notice how the steps fork out after the Installations step? This is to indicate that:
- Exterior painting can happen at any point after the installations
- Interior painting can’t take place until the installations have been completed
- Interior and exterior painting can be performed simultaneously, which means these tasks are parallel
- Furnishing can’t happen until the interior paint job has dried
- The landscaping stage can’t start until the exterior paint job has dried
After completing the diagram, display the dependencies in your List or Gantt View.
Next, we’ll estimate the duration of tasks , writing the number of days in the designated field in List View. Considering that information, we’ll schedule tasks and/or subtasks in Gantt View.
Finally, we’ll calculate the critical path and slack . In our case, there’s little leeway since most activities are crucial.
As you can see in the image above, the only task with slack is the exterior painting. Once the installations are completed, exterior painting can occur at any point, provided enough time is allotted to drying and, eventually, landscaping.
Say there’s been a change of plans, and our flooring contractors asked to reschedule for the following week. In that case, we’ll move the subtask bar to its new spot. With the automatic rescheduling option activated, the other tasks will be updated accordingly! ✔️
Navigate Project Timelines Like a Pro With the Critical Path Method
The critical path method can be an excellent helping hand when dealing with a demanding project. It enables you to meticulously assess and sequence tasks, ensuring that you meet deadlines, keep the project schedule in order, maintain healthy client relationships, and drive actual progress and growth.
When your tasks are sorted out, the rest of the project falls into place.
With a tool like ClickUp , you can try CPM for free and with minimal effort. Get started today! ✨
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How to Find Critical Activities and Tasks in CPM Project Management
By Kate Eby | October 14, 2021
The critical path method (CPM) is a scheduling technique that project managers use to determine the minimum duration and level of flexibility in a project. Learn how to identify critical activities and find insight from experts in our guide.
Included on this page, you’ll find steps for identifying critical activities and visual examples of critical vs. non-critical activities . Plus, you’ll learn about crashing activities in CPM .
What Is Critical Path?
A critical path in project management is the longest possible sequence of dependent tasks that stakeholders must complete on time in order to deliver a project on schedule. By identifying the critical path, you can determine the earliest project completion date.
Essentially, locating the longest sequence of dependencies allows you to find the shortest project duration. Read our guide to the critical path method to learn more about this practice.
“Critical activities are those that will delay the overall project duration, whereas non-critical activities won't delay a project,” said Thomas Jepsen, CEO of home-building platform Passion Plans . “Because of the nature of non-critical activities, you are more free to choose when to start a non-critical activity.”
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What Is a Critical Activity in Project Management?
A critical activity in project management is any task that stakeholders must complete on schedule to meet project deadlines. Delays in one activity will affect subsequent tasks and the entire project unless you can reduce the time on other tasks.
The terms critical activity and critical task are often used interchangeably in project management. There are two types of critical activities:
- Dependent Tasks: This category includes any activities you must complete in a certain order. A predecessor task must start or finish in order for the successor task to start or finish. Dependent tasks are sometimes referred to as sequential activities . As an example, suppose you’re baking a birthday cake. Preheating the oven, baking the cake, and frosting the cake are all dependent tasks because each depends on the completion of the preceding tasks.
- Parallel Tasks: You can run these activities concurrently with other tasks. To use the cake example, preheating the oven and mixing the cake batter could be parallel tasks because you can do them simultaneously. One does not depend on the other to start the task.
The concept of resource constraints , or the limitations on resources you have available for a certain project, is important to understanding critical activity and critical path. Examples of resource constraints include staff hours, budget, equipment, and supplies. More resource constraints result in more dependencies, which lengthen the critical path.
Suppose you’re hosting a dinner party without any assistance. If you’re preparing a main course and a dessert that will each take an hour and you can make only one dish at a time, these tasks become dependencies because they’re constrained by your time. The availability of your kitchen equipment may be another constraint.
But if you enlist a friend to bring dessert, you turn the two responsibilities into parallel tasks. By reducing the constraints on time and kitchen space, you’ve shortened the critical path.
Why Are Critical Path Activities Important?
Critical path activities are often important because they can throw the entire project off schedule. The key distinction between critical vs. non-critical activities is whether a late start or finish will push back the project completion date.
For example, a task may be an important part of a project, but it isn’t considered a critical activity unless completing it late will delay the entire project.
How Do Activities Work in a Critical Path Project Schedule?
Most projects include both dependent and parallel tasks. To develop a schedule, project managers typically identify the following for each activity:
- Earliest Start Date: Identify this date based on the amount of time it would take to complete the dependent tasks immediately preceding it.
- Earliest Finish Date: Assess the minimum amount of time needed to complete the task, and calculate this date based on the projected start date.
- Latest Start Date: Determine the latest date an activity can begin without jeopardizing the project schedule.
- Latest Finish Date: This is the latest date you can complete a task without pushing back the overall project timeline.
Project managers assign each task a float (also referred to as slack ), which is the amount of time the task can be delayed without impacting the project schedule. Activities on the critical path will have zero float.
CPM works best when there’s a high level of certainty about how long critical path activities will take to complete. When project managers aren’t sure of the duration of some tasks, they’ll often use CPM in tandem with the project analysis and review technique (PERT) , another approach to project management.
In PERT, you calculate three durations: the optimistic duration, the most likely duration, and the pessimistic duration. Using a weighted average of the three durations, PERT creates an estimated duration.
How Do You Find Critical Activities?
Before you apply the critical path method, you’ll need to have a well-defined project scope . Use a critical path tracking template to help you plan and adjust the project schedule.
Once you’ve established the goals, budget, and schedule, these following six steps can help you find critical activities in CPM:
- Divide the Project into Tasks: Break down the project into basic activities, keeping a high-level focus. From there, break down activities into more detailed subtasks, then use a work breakdown structure (WBS) to arrange activities further into manageable pieces of work.
- What tasks need to be completed before this task begins?
- What tasks can be completed at the same time as this task?
- What task should begin immediately after this task is completed?
- Best-case scenario, or shortest time frame
- Most likely scenario, or most realistic time frame
- Worst-case scenario, or longest time frame
Seek feedback when scheduling tasks using CPM.
“Reviewing your critical activities with key stakeholders is crucial,” says Jepsen. “While the underlying ideas may be rather simple to follow in a diagram, it's important to understand that you're working with human beings. In the real world, you're operating in a dynamic situation where initial project detail assumption may not hold. Perhaps your main engineer falls sick. What do you do then?”
- Use your network diagram and draw the longest path through the network.
- Use the forward pass/backward pass method , in which you identify the earliest start and finish times, along with the latest start and finish times.
- Update the Critical Path Diagram Throughout the Project: As the team completes activities over the course of the project, update your diagram to show the actual time for completion rather than your projections. Doing so will help you create a more realistic schedule as the project progresses and, possibly, identify a new critical path.
Examples of Critical Path Activities
These examples demonstrate easy visual examples of critical path activities/tasks versus non-critical path activities/tasks. We’ve broken out the tasks that must happen in a particular sequence (critical) vs. those that don’t (non-critical).
Example #1: Baking a Birthday Cake
- Mix the batter (A)
- Pour the batter into the pan (B)
- Bake the cake for 20 minutes (D)
- Frost the cake (G)
- Add and light the candles (H)
- Preheat the oven for 15 minutes (C)
- Make the frosting (E)
- Count the candles (F)
A: Mixing the batter B: Pouring the batter into the pan C: Preheating the oven for 15 minutes D: Baking the cake for 20 minutes E: Making the frosting F: Counting the candles G: Frosting the cake H: Adding and lighting the candles
The critical path for baking a cake is A, B, D, G, H.
Example #2: Publishing a Book
- Create a book proposal (A)
- Write the book (B)
- Edit the book (D)
- Print the book (G)
- Distribute the book to booksellers (H)
- Illustrate the book (C)
- Design the cover (E)
- Market the book (F)
The critical path for publishing a book is A, B, D, G, H.
Example #3: Building a Website
- Choose a domain name (A)
- Create a site map (B)
- Choose a CMS (C)
- Design the website (F)
- Develop preliminary content (G)
- Publish the website (I)
- Train for staff and clients (D)
- Install an analytics program (E)
- Develop a marketing plan (H)
- Generate user feedback (J)
The critical path for building a website is A, B, C, F, G, I.
What Is a Crashing Activity in Critical Path?
A crashing activity in critical path management is a strategy of adding resources to an activity, potentially resulting in a new critical path. Project managers may use crashing to speed up the timeline or when a project is behind schedule.
For example, if a storm delays a critical task in a construction project , you may crash an activity by hiring additional contractors, reallocating staff who are working on a different activity or project, or paying overtime to stay on schedule.
An alternative to project crashing is fast tracking , in which the team completes activities in parallel. Project managers typically use crashing after fast tracking has failed.
Critical Activities vs. Critical Path
A project’s critical activities are those that have zero float , meaning any delay in completion delays the entire project. In contrast, the critical path maps the longest path through all critical activities from start to finish in a project.
Returning to the cake-baking example, mixing the cake batter and baking the cake are activities with zero float. Any delay in either task would delay the completion of the cake.
For a real-world example in project management, suppose you are obtaining permits for a construction project. You need to obtain permits to begin site work, so if permitting takes longer than you expected, the entire project schedule will be thrown off track.
As an example of critical activities, say you are planning an event budget. Until you make the budget, you can’t book a venue, sign contracts with vendors, or market the event.
What Is a Critical Task in Project Management?
A critical task in project management is an activity that must be completed on schedule to avoid delaying a project. This is the same as a critical activity.
What Are Critical Flags in a Critical Path?
A critical flag is a mark applied to tasks that you deem critical using project management software. You can apply a critical flag to a task if it affects the duration of the overall project. Otherwise, the task is considered non-critical.
When to Apply a Critical Flag to an Activity or Task
Apply a critical flag to any task with a total float of zero or a negative float, which occurs when a task’s schedule must be compressed in order to complete the project on time.
Project managers will often create multiple critical paths during a project because delays may make tasks that were originally non-critical activities into critical activities. It’s essential that you closely monitor critical tasks, along with any linked non-critical tasks that are at risk of becoming critical.
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Show the critical path of your project in Project
Every task is important, but only some of them are critical . The critical path is a chain of linked tasks that directly affects the project finish date. If any task on the critical path is late, the whole project is late.
The critical path is a series of tasks (or sometimes only a single task) that controls the calculated start or finish date of the project. The tasks that make up the critical path are typically interrelated by task dependencies. There are likely to be many such networks of tasks throughout your project plan. When the last task in the critical path is complete, the project is also complete.
Learn more about critical path analysis .
Show the critical path in the Gantt Chart view
The Gantt Chart view will likely be your most used view for showing the critical path.
Choose View > Gantt Chart .
Choose Format , and then select the Critical Tasks check box.
Tasks on the critical path now have red Gantt bars.
Show the critical path in other task views
You can see the critical path in any task view by highlighting it.
On the View tab, pick a view from the Task Views group.
Staying on the View tab, select Critical from the Highlight list. The critical path shows up in yellow.
To see only the tasks on the critical path, choose the Filter arrow, then pick Critical .
Tip: In a Network Diagram, tasks on the critical path automatically show up in red. No highlighting is needed.
Video: Show the critical path
This video demonstrates how to display the critical path in your project, in both the Gantt Chart view and other views.
View the critical path in a master project
When you’re managing a master project, whole subprojects can be on the critical path. You can see if this is true by telling Project to treat the subprojects like they are summary tasks.
Choose File > Options .
Choose Schedule , and then scroll down to the Calculation options for this project area.
Make sure the Inserted projects are calculated like summary tasks box is selected.
Tip: This setting does not affect other projects. That is, it only applies to the master project you’re working on.
Change what tasks show up on the critical path
Typically, critical tasks have no slack. But you can tell Project to include tasks with one or more days of slack on the critical path so you can see potential problems coming from farther away.
Choose Advanced , and then scroll down to the Calculation options for this project area.
Add a number to the Tasks are critical if slack is less than or equal to box.
Top of Page
Show multiple critical paths
You can set up your project schedule to display as many critical paths as you need to keep tabs on your project.
Choose Advanced , scroll down to the bottom, and then select Calculate multiple critical paths .
Choose Format , and then select Critical tasks .
By default, Project shows only one critical path, the one that affects the project’s finish date. But you might need to see more than one for a couple reasons:
To make sure each subproject of a master project is on time.
To track the progress of different phases or milestones.
To keep an eye on any series of tasks for any reason.
Project management tip: When viewing multiple critical paths, don’t forget that there's still only one main critical path. If it falls behind schedule, the whole project falls behind schedule. Try these tips to make better use of multiple critical paths in a project once you’ve set them up.
More about critical path analysis
If you have saved a baseline for your project, the critical path can show you if your project will finish on time and where the danger points are. To get the most out of critical path analysis:
Regularly view the critical path. Be aware that the critical path can change from one series of tasks to another as you progress through the schedule. The critical path can change as critical tasks are completed or as other series of tasks are delayed.
Closely monitor critical tasks. Any task on the critical path is a critical task. Monitor these tasks regularly to see if any of them slip. If a critical task slips, so does your finish date. Save a baseline and use the Tracking Gantt view to see slipped tasks.
Review series of tasks that may become the critical path. If a non-critical series of linked tasks slips its dates enough, that series of tasks will become the critical path. You can view other potentially risky tasks by showing multiple critical paths in a project .
Protect yourself by viewing tasks that can slip without affecting the critical path. By default, the critical path shows the tasks that cannot slip at all or the project date will slip. You may want to view tasks that currently can slip by a day without affecting the critical path, because if they slip by more than a day, they will become critical tasks. Viewing these tasks with slack helps alert you to tasks that are becoming critical while you still have some buffer.
Tip: To change the sensitivity of critical tasks, choose File > Options > Advanced . In the Tasks are critical if slack is less than or equal to list, enter the number of days under which a task will be considered critical.
When you display the project's critical path , Project shows only a single, overall critical path, which is the only critical path that controls the project's finish date. However, you can set up your plan so that you can also see an additional critical path for each independent network or each series of tasks. You might find this useful for keeping track of each of the subprojects within a master project, or of each phase or milestone of a project that is divided into multiple phases.
By knowing and tracking the critical path for your project, as well as the resources that are assigned to each critical task, you can identify the tasks that can affect your project's finish date and thus discover whether your project will finish on schedule.
Learn more by reading Manage your project's critical path .
These instructions are specific to Project 2007.
Display the critical path for your project
To verify that adjustments that you make to the project plan don't adversely affect the critical path, you can review the critical path and critical tasks in any of several ways.
Note: By default, Project 2007 does not display a project's critical path.
Change which tasks are defined as critical
In Project 2007, a critical task has zero days of slack (float). However, you can change this default value and define a task as critical that has, for example, one or two days of slack.
On the Tools menu, choose Options , and then select the Calculation tab.
In the Tasks are critical if slack is less than or equal to box, enter the maximum amount of slack, in days, that you want to use to define critical tasks.
If you want this value to be the default value for all of your projects, choose Set as Default .
To learn how to find a task's slack, see Show slack in your project .
For instructions about changing a task's slack, see Set lead or lag time (float) between tasks .
Tip: To change the sensitivity of critical tasks, on the Tools menu, choose Options . On the Calculation tab, under Tasks are critical if slack is less than or equal to , specify the number of days under which a task will be considered critical.
When you display the project's critical path , Project 2007 shows only a single, overall critical path, which is the only critical path that controls the project's finish date. However, you can set up your plan so that you can also see an additional critical path for each independent network or each series of tasks. You might find this useful for keeping track of each of the subprojects within a master project, or of each phase or milestone of a project that is divided into multiple phases.
In Project for the web, you can view the critical path by using a filter.
When Show Critical Path is on, you'll see the critical path for your project highlighted red in the timeline.
Manage your project's critical path
View and track scheduling factors
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Critical Path Method for Project Management
By Wrike Team , September 2, 2023 - 10 min read
The Critical Path Method (CPM) is a vital project management tool that represents the most extended sequence of tasks that must be accomplished to ensure the completion of the entire project.
You can determine the critical path by measuring the longest sequence of dependent activities from start to end.
It can be visually represented by using a Gantt Chart software that can help build a visual timeline of the project.
In this article, we’ll detail in depth the steps for using critical path method for project management, explain how to calculate the length of your project, explain how keeping an up-to-date project schedule allows you to have flexibility within your critical path, and share our helpful project scheduling template to get you started.
What is the critical path method?
The CPM is a sophisticated project management technique to plan, schedule, and manage complex projects. It involves identifying all the tasks needed to complete a project, determining the sequence in which these tasks must be carried out, and then calculating the most prolonged duration of time it will take to complete the project from start to finish. This most prolonged duration is known as the ‘critical path,’ and it provides a clear timeline for project completion.
In CPM, tasks are categorized as ‘critical’ and ‘non-critical.’ Critical tasks must be completed on time to ensure the project is finished on schedule. Any delay in a crucial task will result in a delay in the project. Non-critical tasks, on the other hand, have some flexibility in their scheduling so they’re less likely to cause a delay in the project completion.
CPM is especially valuable for projects with numerous interdependent activities, as it allows project managers to see where potential bottlenecks may occur and where resources can be allocated most effectively. By identifying the critical path, project managers can prioritize tasks, mitigate risks, and better ensure timely project completion.
Benefits of using critical path method in project management
CPM offers many benefits that can significantly enhance the effectiveness of project management.
- Provide a clear visualization of the project timeline. By illustrating the sequence and duration of each task, CPM allows project managers to gain a comprehensive understanding of the project’s flow, making it easier to plan and manage resources effectively.
- CPM’s ability to identify critical tasks. This not only helps in prioritizing tasks but also allows for the proactive management of potential delays. By understanding which jobs have the flexibility to be delayed without affecting the overall timeline, project managers can better manage changes or issues that arise during the project life cycle.
- CPM aids in risk identification and mitigation. Highlighting the critical path allows project managers to foresee potential bottlenecks or delays and proactively mitigate these risks. This can lead to a significant reduction in project downtime and associated costs.
- CPM promotes better communication within the project team. With a clear visual representation of the project’s timeline, team members can better understand their roles, responsibilities, and the impact of their tasks on the overall project. This can lead to improved collaboration, efficiency, and overall project success.
In summary, the CPM is an indispensable tool in project management, offering enhanced planning, risk mitigation, resource management, and team collaboration capabilities.
How to find the critical path in a project
Step 1: Identify all tasks required to complete the project
Start by listing all the functions or activities that need to be completed for the project’s successful conclusion, also known as a work breakdown structure . When created thoroughly, the work breakdown structure is a roadmap that guides a team when completing projects — whether simple or complex. Here’s a powerful work breakdown structure example from Wrike.
Step 2: Determine the sequence of tasks
Next, identify the order in which the tasks need to be performed. Some tasks may depend on the completion of others before they can begin, while others may be carried out concurrently. This step is crucial in understanding the dependencies and relationships between tasks.
Step 3: Estimate the duration of each task
Assign a time estimate to each task. This should be the total time required to complete each task from start to finish. Make sure to account for any potential delays or issues that may arise.
Step 4: Draw a network diagram
Using the information from the previous steps, draw a network diagram. This visual representation should depict all the tasks, their sequence, and their dependencies. Each task is represented as a node on the diagram, and the arrows between nodes represent the dependencies between tasks.
Step 5: Identify the critical path
The critical path is the longest path from the start to the end of the project, passing through all the essential tasks to the project’s completion. In other words, the sequence of tasks determines the minimum time needed to complete the project. On your network diagram, the critical path is the longest from the initial to the final task.
Step 6: Calculate the float
The float or slack is how long you can delay a task without waiting for the project. Tasks on the critical path will have zero float, meaning they can only be postponed without impacting the project timeline. However, non-crucial tasks may have some float, allowing for some flexibility in scheduling.
Step 7: Monitor the critical path
Once the project is underway, closely monitoring the tasks on the critical path is essential. Any delays in these tasks will directly impact the project timeline. Regularly updating and reviewing the critical way can help identify potential issues early and keep the project on track.
Consider using Wrike’s critical path method template to augment this process further. This pre-structured template simplifies identifying your project’s critical path, saving time and enhancing project planning efficiency.
Try our template
Critical path method example
Now we’ll try to demonstrate the concept of the critical path method with a simple, real-life example: planning a killer party. How should you plan and execute this project?
1. Define the project scope
First, we need to define all of the tasks that must be finished to complete the project. For our party example, it might look like this:
- Choose a date and venue
- Make the ultimate playlist
- Set up the sound system
- Invite your friends
- Buy the food and drinks
- Cook your famous casserole
- Host the party
When we look at these tasks individually, we realize that some of them cannot be started before the others are completed. That is, some tasks are dependent on others. We’ve designated these relationships in the table below:
The actions “invite your friends,” “buy the food and drinks,” “cook your casserole,” and “host the party” form a sequence of tasks that must be performed in a specific order, one right after the other, to ensure a successful result. Such tasks are called sequential activities.
Together with the start of our project (“choose a date and venue”), these tasks are the most critical steps in completing our project. Thus, these actions will be placed on the critical path.
2. Define different project paths
You can have more than one critical path in a project so that several paths run concurrently. This can result from multiple dependencies between tasks or separate sequences that run for the same duration.
In planning a party, various project paths will consist of tasks that need to be completed. For example, one path could involve tasks related to booking the venue, such as researching options, visiting potential locations, and finalizing the booking. Another path might focus on the catering, which includes deciding the menu, finding a caterer, and arranging the food and drink delivery. Another path could be about entertainment, involving tasks like hiring a DJ or band and planning games or activities.
While separate, each of these paths is an integral part of the overall project and must be coordinated effectively to ensure a successful party. By clearly defining these different project paths, you can better manage the tasks and timelines associated with each one.
3. Consider the resource constraints
Traditional critical path schedules in project management are based only on causal dependencies. We’ve already marked these dependencies in our plan. (e.g., it’s impossible to cook the casserole without buying the ingredients). However, a project may have limited resources that need to be taken into consideration, such as how to calculate load in resource planning. These limitations will create more dependencies, often referred to as resource constraints .
If you work on a team, you may split the project work between team members. In our example, while you’re choosing a date and venue and inviting people, one of your friends can make a playlist, and another can get the food and drinks. The tasks can be done in parallel, as in our chart above.
However, if you’re the only person responsible for the project, you have a resource constraint because you can’t be in two places at the same time. In this case, your critical path will look different.
On the chart above, we assume you first need to choose the date and venue, and only later can you make a playlist. However, depending on the project conditions, these tasks can be performed in a different order.
4. Calculate the length of your project
L et’s assume you have to do everything by yourself. We estimated the length of time each activity will take. Also, we determined the approximate start time for each task on the critical path. Here’s what we came up with:
Now, if we add up all of our critical tasks’ duration, we’ll get the approximate time we need to complete the whole project. In our case, three days and six hours, since “make the ultimate playlist” and “set up the sound system” are not on the critical path. If we add the duration to the start time, we can calculate the earliest project completion time. Understanding the CPM allows us to make this calculation quickly and accurately.
5. Leave space for flexibility
The critical path method was developed for complex but fairly predictable projects. However, in real life, we rarely get to manage such projects. Let’s say you plan to redecorate your living room with a friend.
Your task list may look like this:
- Get rid of the old furniture
- Paint the walls
- Fix the ceiling
- Install the new furniture
Your friend’s responsibilities are to:
- Choose the new curtains
- Hang the new curtains
T he curtain tasks form a sub-project and can be treated as a non-critical path. Your friend can “choose the new curtains” and “hang the new curtains” any time before the end of your project. The curtain tasks have flexibility in the start and end date, considered float. These tasks are parallel and will not be placed on the critical path. Here’s how this project would look on a Gantt chart :
If any of the parallel tasks were to be significantly delayed, it would prevent our whole project from being completed on time. Therefore, you should always keep an eye on similar tasks.
6. Adjust to the changes in the critical path
Let’s assume that choosing the curtains took our friend longer than we initially expected. This will delay the end of the project.
Our redecoration is incomplete without the new curtains, so the path that previously was non-critical becomes critical. The initial critical path changes.
To monitor your non-critical tasks, your project schedule must be current. That’s the only way you’ll know exactly where your project is at any given moment and whether it will be delivered as initially planned.
Critical path method vs. PERT
In project management, the CPM and the Program Evaluation and Review Technique (PERT) are valuable tools. However, they each have distinct characteristics and are better suited to different types of projects.
CPM is a deterministic approach that assumes a fixed time frame for each task. This makes it ideal for projects with well-known task durations and little variability, like construction or manufacturing projects. CPM focuses on the critical path, the sequence of tasks that determines the project’s shortest duration. By identifying this path, CPM allows project managers to prioritize tasks directly impacting the project’s timeline.
PERT is similar to the critical path in that they are both used to visualize the timeline and the work that must be done for a project. However, with PERT, you create three different time estimates for the project:
- The shortest possible amount of time each task will take
- The most probable amount of time
- The most extended amount of time tasks might take if things don't go as planned
This makes PERT ideal for research and development projects or any other project with uncertain task durations. While both methods help in project planning and scheduling, PERT’s ability to handle uncertainty makes it more flexible in the face of potential changes or delays. CPM’s focus on the critical path can make managing and controlling tasks critical to the project’s timeline easier.
The choice between CPM and PERT should be based on the nature of your project and the level of certainty or uncertainty in task durations. Both methods offer valuable insights that can help drive project success.
CPM success story
The Hoover Dam , constructed between 1931 and 1936, is a testament to effective project management’s power. While the critical path method hadn’t been formally defined yet, its principles were applied during the dam’s construction.
The project had many activities, each with dependencies and timelines. The project managers had to coordinate these activities in such a way as to ensure the project was completed on time and within budget. They effectively identified the project’s critical path, focusing resources and attention on the tasks that would cause the most significant delays if not completed on time.
The Hoover Dam was completed two years ahead of schedule despite the project’s complexity. This early completion was primarily due to the effective use of what we now know as the critical path method, making it a compelling case study for successfully implementing this technique.
This case study provides a practical example of the critical path method in action and illustrates its potential in managing large-scale, complex projects.
How Wrike can help you with your critical path management
Determining the critical path of a project isn’t exactly a quick process. That’s why we’ve designed a pre-built template for project scheduling that will help you progress through the steps of creating your critical path. Our project scheduling template allows our customers to visualize the critical path on a Gantt chart, assign tasks to team members, and drag and drop activities to ensure proper resource management.
Ready to use Wrike for your critical path analysis?
Here are some further resources you can use to brush up on your critical path method knowledge:
- The Critical Path Method , Seminar, Stanford
- Explaining the Critical Path Method , U.S. Department of Health and Human Services
- The ABCs of the Critical Path Method by Harvard Business Review
How to Use a Single Gantt Chart for Multiple Projects
- When to Use a Project Calendar vs. a Gantt Chart
What Is a PMO? (Guide & Infographic)
What is a PMO? A “project management office” is defined as an internal or external group
Using a single Gantt chart to view for multiple projects can change your project
What It Means to Be a Digital Project Manager
Today's most effective project managers are the ones who have moved their teams and
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Understanding critical paths in project management
A critical path is a method used by project managers to prioritize tasks and deliver a project on time. But unlike most project management concepts, the title of this one doesn’t give much away.
That’s why we’ve created this no-nonsense guide to help you understand what critical paths are, why they’re important, and how to implement them. Plus, we’ll show you how the critical path feature in monday work management can make your job easier.
What is a critical path?
A critical path is the longest sequence of dependent tasks that must be completed to execute a project. The tasks are called critical activities because the whole project runs over if they’re delayed.
For example, if you’re building a house, the critical path might include activities like digging the foundations, building the walls, and installing the roof. If any of these critical activities fall behind schedule the whole project gets delayed.
Project managers use the critical path method (CPM) to find the critical path. The CPM — also known as critical path analysis (CPA) — is a project management technique used to plan and schedule complex projects. It’s an algorithm that identifies the longest sequence of dependent activities and measures the time required to complete them from start to finish.
What does a critical path look like?
Asking what a critical path looks like is like asking, “how long is a piece of string?” — i.e. there’s no definitive answer.
Traditionally, the critical path was a flow chart. For example, some house-building activities take longer than others, so the critical path highlights the longest duration:
A more complex diagram might look like this:
Nowadays, other more visually appealing ways of presenting a critical path exist. For example, using a Gantt chart allows you to visualize the critical activities:
Critical path vs. critical chain
Critical path and critical chain are two different approaches to completing a project.
The critical chain methodology pinpoints the bottlenecks or limiting factors that can cause businesses to miss project deadlines. It focuses on monitoring the use of resources — like materials and labor. For example, a project manager might delay the start of one task so that a skilled worker does not have to perform two tasks at the same time.
The critical path focuses on task management, assumes unlimited resources, and identifies the longest track of tasks. It helps identify tasks that may cause project delays and guides project managers to take preventive measures from the start.
On the other hand, the critical chain focuses on resource and buffer management, assumes limited resources, and identifies the longest chain of dependent events. It inserts buffers between dependent events to protect the project from delays.
Critical path vs. critical activity
Critical path and critical activity are related concepts in project management , both determined by the critical path method (CPM).
The critical path is the longest sequence of tasks that must be completed for the project and comprises critical activities. Any delay in completing tasks on the critical path will also delay the project.
A critical activity is a specific scheduled activity that is part of the critical path. It’s essential to the project’s timeline, and any delay in completing a critical activity will delay the entire project.
For example, if it takes twice as long to dig the foundations for a new house, then the entire house building project gets delayed. A critical activity typically has zero float, meaning there’s no flexibility in the start or finish dates.
Critical path vs. PERT
The critical path and PERT (Program Evaluation and Review Technique) are tools for planning and controlling projects.
PERT is a framework to map out task dependencies and estimate how long a project will last. It’s a statistical tool to visualize the overall project schedule — not just the critical path — and shows the relationship between tasks as well as the overall project duration.
For example, a project with seven key activities and a total project duration of 14 days, could have a chart that looks like this:
The critical path is used to schedule and manage project tasks, focusing on the longest sequence of tasks and considering task dependencies and slack time. It is suitable for projects with predictable task durations.
On the other hand, PERT is used to calculate the time required to complete project activities, especially when task durations are variable and uncertain. It allows for flexibility in project scheduling and focuses on time estimation and uncertainty.
Critical path vs. Gantt chart
The critical path and Gantt chart are both project management visualization tools, but they serve different purposes.
The critical path helps schedule and manage project tasks, taking into account task dependencies and slack time. It’s suitable for projects with predictable task durations.
On the other hand, a Gantt chart provides a visual overview of tasks, durations, and dependencies in a project schedule. It helps track progress, allocate resources, and communicate project timelines.
While a Gantt chart can highlight the critical path, its primary purpose is to visualize the project schedule.
What are the benefits of the critical path method?
The critical path method (CPM) offers improved project planning, enhanced scheduling, clearer communication, effective resource management, tighter cost control, risk detection, and better project management.
1. Enhances project planning
The CPM provides a structured approach to project planning by identifying the sequence of activities and their dependencies. This helps project managers create a realistic and robust project schedule .
2. Helps prioritize tasks
The CPM identifies the critical tasks and determines the critical path. This helps project managers prioritize tasks effectively and determine where and how to allocate resources.
3. Improves team communication
The CPM requires input from key stakeholders, including team members and subcontractors. This collaboration ensures everyone understands the project timeline and dependencies, leading to better communication and coordination.
4. Facilitates more effective resource management
The CPM helps project managers identify resource requirements for each activity. Project managers can allocate resources efficiently by understanding the critical path and resource dependencies, minimizing bottlenecks and unexpected delays.
5. Tightens cost control
The CPM assists project managers in controlling costs by allocating the right resources to the right places. This reduces the chances of unexpected delays that may incur additional costs.
6. Detects potential risks
The CPM allows project managers to identify potential risks and their impact on the project schedule. By analyzing the critical path and considering the float or slack time, project managers can predict the effects of delays and make adjustments to mitigate risks.
7. Improves project management
The CPM enables project managers to clearly communicate project plans, schedules, and performance. This clarity helps them monitor progress, identify issues, and make informed decisions.
To summarize: by utilizing the CPM, project managers can optimize project timelines, allocate resources effectively, and mitigate risks, leading to successful projects.
How to find the critical path
Now, let’s identify the critical path from start to finish.
1. List all your project tasks
Before you even think about a critical path, you need to list what tasks to include in the project — i.e. your work breakdown structure .
Spend some time speaking with stakeholders to confirm the project details. Once you have all the information, you can identify all the activities that must happen to complete the project.
2. Put all the tasks in order
Once you’ve identified the tasks, it’s time to put them in chronological order and identify any task dependencies . This will help you work out the project timeline.
So what’s the best way to put them in order?
Whether you’d prefer to create a project roadmap, tracker, or overview, using an efficient, easy-to-use work management software — like monday work management — simplifies the process by giving you a clear visualization of all your tasks:
3. Estimate how long each task will take
There are several ways to estimate activity duration. To save you from sifting through all the methods out there, we’ve outlined our top three:
- Bottom-up estimating : Add up the estimates of the lowest-level work tasks to arrive at your summary total. Bottom-up estimates take more time to complete, but they also are more accurate than other estimates.
- Comparative estimating : Base your estimates on similar work or projects completed in the past. If you used time tracking in previous tasks, you’ll see precisely how long they took.
- Parametric estimating : Calculate a portion of the work and then multiply to get the overall estimate — e.g. if you believe one ad takes 2 hours and you have five ads to do, it should take 10 hours in total.
Read also: Bottom-up vs. top-down
4. Find all the potential ‘paths’ or ‘strings’
Any project can have multiple paths or strings of connected and dependent tasks.
This part of the process involves finding all these possible paths and calculating how long each one will take so that you can pinpoint the one with the longest duration.
By hand, this can be a headache with a high chance of error, which is not ideal. Fortunately, project management platforms, like monday work management, can do this automatically.
5. Identify the critical path
Now for the main event — it’s time to find the critical path.
Once you — or your work management software — have listed all the paths and strings, you need to identify the longest path through the project from start to finish.
So, if you’ve got a string of tasks that takes eight days, one that takes six days, and another that takes 12, then the 12-day string is the critical path. It’s the one that can’t have any delays without moving out your project end date.
6. Monitor the critical path
The critical path can, and most likely will, change throughout the project. Some tasks may take longer than expected, or new tasks get added over time.
Any changes to the project can have a knock-on effect on the critical path. This means you’ll need to check continuously throughout the project and update your critical path diagram accordingly.
We know it’s not ideal. One of the limitations of using the critical path project management method is its lack of flexibility. That’s why we created a critical path feature in monday work management that accounts for more flexibility.
Manage your critical paths with monday work management
The monday work management critical path feature makes your team more aware and efficient by visually displaying each project’s duration.
Once you add this feature to your Gantt Chart, it highlights the critical path in your project’s timeline — the events that must be completed on time for the overall project to finish on schedule.
Moreover, the software monitors any changes in critical path activity and automatically updates the current critical path in your project plan , so you don’t have to.
Start identifying critical paths today
So there you have it — a simple, no-nonsense guide to critical paths, including their definition, benefits, and how to identify them in your projects.
Now you know what’s what, why not check out some project management software that enables you to implement critical paths within your projects?
Critical path FAQs
Why is the critical path important in project management.
The critical path is important in project management because it helps estimate the project duration accurately, identify critical activities that must be completed on time, and highlight task dependencies, resource constraints, and potential risks.
What are non-critical activities?
Non-critical activities are tasks that can be delayed beyond their allotted deadline without affecting the project's overall duration. These activities have slack time and are not part of the critical path.
Can a project have multiple critical paths?
Yes, a project can have multiple critical paths. In complex projects, you can have multiple sequences of activities that are equally critical and must be completed on time for the project to run on schedule.
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The ABCs of the Critical Path Method
- F. K. Levy,
- G. L. Thompson,
- J. D. Wiest
Recently added to the growing assortment of quantitative tools for business decision making is the Critical Path Method—a powerful but basically simple technique for analyzing, planning, and scheduling large, complex projects. In essence, the tool provides a means of determining (2) which jobs or activities, of the many that comprise a project, are “critical” in […]
Recently added to the growing assortment of quantitative tools for business decision making is the Critical Path Method—a powerful but basically simple technique for analyzing, planning, and scheduling large, complex projects. In essence, the tool provides a means of determining (2) which jobs or activities, of the many that comprise a project, are “critical” in their effect on total project time, and (2) how best to schedule all jobs in the project in order to meet a target date at minimum cost. Widely diverse kinds of projects lend themselves to analysis by CPM, as is suggested in the following list of applications:
- FL Ferdinand K. Levy has just become Assistant Professor at Stanford University.
- GT Gerald L. Thompson is Professor of Applied Mathematics and Industrial Administration, Carnegie Institute of Technology.
- JW Jerome D. Wiest is Assistant Professor, University of California at Los Angeles.
- Project management |
- Critical path method: How to use CPM fo ...
Critical path method: How to use CPM for project management
The critical path method is a technique that allows you to identify tasks that are necessary for project completion. The critical path in project management is the longest sequence of activities that must be finished on time to complete the entire project. Below, we break down the steps of how you can find the critical path for your next project.
Building out a project roadmap can help you visualize what needs to be done to reach your end goal. The critical path method helps you do exactly that. It’s a project management technique that involves mapping out key tasks or critical tasks necessary to complete a project.
What is the critical path method (CPM)?
The critical path method (CPM) is a technique where you identify tasks that are necessary for project completion and determine scheduling flexibilities. A critical path in project management is the longest sequence of activities that must be finished on time in order for the entire project to be complete. Any delays in critical tasks will delay the rest of the project.
CPM revolves around discovering the most important tasks in the project timeline, identifying task dependencies, and calculating task durations.
CPM was developed in the late 1950s as a method to resolve the issue of increased costs due to inefficient scheduling. Since then, CPM has become popular for planning projects and prioritizing tasks. It helps you break down complex projects into individual tasks and gain a better understanding of the project’s flexibility.
Why use the critical path method?
CPM can provide valuable insight on how to plan projects, allocate resources, and schedule tasks.
Here are some reasons why you should use this method:
Improves future planning: CPM can be used to compare expectations with actual progress. The data used from current projects can inform future project plans.
Facilitates more effective resource management : CPM helps project managers prioritize tasks, giving them a better idea of how and where to deploy resources.
Helps avoid bottlenecks: Bottlenecks in projects can result in lost valuable time. Plotting out project dependencies using a network diagram, will give you a better idea of which activities can and can’t run in parallel, allowing you to schedule accordingly.
How to find the critical path
Finding the critical path involves looking at the duration of critical and non-critical tasks. Below is a breakdown of the steps with examples.
1. List activities
Use a work breakdown structure to list all the project activities or tasks required to produce the deliverables. The list of activities in the work breakdown structure serves as the foundation for the rest of the CPM.
For example, let’s say the marketing team is producing a new interactive blog post. Here are some tasks that might be in the work breakdown structure:
Once you have a high-level idea of everything that needs to be done, you can start identifying task dependencies.
2. Identify dependencies
Based on your work breakdown structure, determine the tasks that are dependent on one another. This will also help you identify any work that can be done in parallel with other tasks.
Here are the task dependencies based on the example above:
Task B is dependent on A
Task C is dependent on B
Tasks C and D can run in parallel
Task E is dependent on D
Task F is dependent on C, D, and E
The list of dependent tasks is referred to as an activity sequence, which will be used to determine the critical path.
3. Create a network diagram
The next step is to turn the work breakdown structure into a network diagram, which is a flowchart displaying the chronology of activities. Create a box for each task and use arrows to depict task dependencies.
You’ll add other time-bound components to the network diagram until you have the general project schedule figured out.
4. Estimate task duration
To calculate the critical path, the longest sequence of critical tasks, you first need to estimate the duration of each activity.
To estimate the duration, try:
Making educated guesses based on experience and knowledge
Estimating based on previous project data
Estimating based on industry standards
Alternatively, try using the forward pass and backward pass technique:
Forward pass: This is used to calculate early start (ES) and early finish (EF) dates by using a previously specified start date. ES is the highest EF value from immediate predecessors, whereas EF is ES + duration. The calculation starts with 0 at the ES of the first activity and proceeds through the schedule. Determining ES and EF dates allows for early allocation of resources to the project.
Backward pass: This is used to calculate late start (LS) and late finish (LF) dates. LS is LF - duration, whereas LF is the lowest LS value from immediate successors. The calculation starts with the last scheduled activity and proceeds backward through the entire schedule.
The early and late start and end dates can then be used to calculate float, or scheduling flexibility of each task.
5. Calculate the critical path
Calculating the critical path can be done manually, but you can save time by using a critical path algorithm instead.
Here are the steps to calculate the critical path manually:
Step 1: Write down the start and end time next to each activity.
The first activity has a start time of 0, and the end time is the duration of the activity.
The next activity’s start time is the end time of the previous activity, and the end time is the start time plus the duration.
Do this for all the activities.
Step 2: Look at the end time of the last activity in the sequence to determine the duration of the entire sequence.
Step 3: The sequence of activities with the longest duration is the critical path.
Using the same example above, here’s what the critical path diagram might look like:
Once you have the critical path figured out, you can build the actual project schedule around it.
6. Calculate the float
Float, or slack, refers to the amount of flexibility of a given task. It indicates how much the task can be delayed without impacting subsequent tasks or the project end date.
Finding the float is useful in gauging how much flexibility the project has. Float is a resource that should be used to cover project risks or unexpected issues that come up.
Critical tasks have zero float, which means their dates are set. Tasks with positive float numbers belong in the non-critical path, meaning they may be delayed without affecting the project completion date. If you’re short on time or resources, non-critical tasks may be skipped.
Calculating the float can be done with an algorithm or manually. Use the calculations from the section below to determine the total float and free float.
Total float vs. free float
Here’s a breakdown of the two types of float:
Total float: This is the amount of time that an activity can be delayed from the early start date without delaying the project finish date or violating a schedule constraint. Total float = LS - ES or LF - EF
Free float: This refers to how long an activity can be delayed without impacting the following activity. There can only be free float when two or more activities share a common successor. On a network diagram, this is where activities converge. Free float = ES (next task) - EF (current task)
There are a few good reasons why project managers benefit from having a good understanding of float:
It keeps projects running on time: Monitoring a project’s total float allows you to determine whether a project is on track. The bigger the float, the more likely you’ll be able to finish early or on time.
It allows you to prioritize : By identifying activities with free float, you’ll have a better idea of which tasks should be prioritized and which ones have more flexibility to be postponed.
It’s a useful resource: Float is extra time that can be used to cover project risks or unexpected issues that come up. Knowing how much float you have allows you to choose the most effective way to use it.
How to use the critical path method
CPM provides visibility into your project’s progress, allowing you to monitor tasks and their completion times. Below are some additional applications of CPM.
Though not ideal, there are times when project deadlines may be pushed up. In those situations, there are two schedule compression techniques you can use: fast tracking and crashing.
Fast tracking: Look at the critical path to determine activities that can be performed simultaneously. Running parallel processes will speed up the overall duration.
Crashing: This process involves allocating more resources to speed up activities. Before obtaining more resources, make sure that it would still be within the project scope and let the stakeholders know of any changes.
Having the critical path plotted out can help you choose the appropriate strategy to meet updated deadlines.
Resolve resource shortages
Keep in mind that CPM doesn’t take resource availability into account. When there is a resource shortage, like an overbooked team member or lack of equipment, you can use resource leveling techniques to solve the issue.
These techniques aim to resolve resource overallocation issues and ensure that a project can be completed with the resources that are currently available.
Resource leveling works by adjusting project start and end dates, so you may have to readjust the critical path or apply this technique to activities with float.
Compile data for future use
The schedule created from CPM is subject to change since you’re working with educated estimates for activity durations. You can compare the original critical path to the actual critical path as the project runs.
This data can be used as a reference to get more accurate task duration estimates for future projects.
Critical path method vs. PERT
CPM and Project Evaluation and Review Technique (PERT) were both developed in the 1950s. PERT is used to estimate uncertainty around project activities by applying a weighted average of optimistic and pessimistic. It evaluates the time needed to complete an activity.
PERT uses three estimates to find a range for the duration of an activity:
Most likely estimate (M)
The calculation for PERT is: Estimated time = (O + 4M + P) / 6
The main difference between PERT and CPM is their level of certainty around activity durations—PERT is used to estimate the time required to complete activities, whereas CPM is used when the activity durations are already estimated.
Let’s see how the two techniques compare:
PERT manages uncertain project activities, CPM manages predictable project activities.
PERT focuses on meeting or minimizing project duration, CPM focuses on time-cost-trade offs.
PERT is a probabilistic model, CPM a deterministic model.
PERT has three estimates for each activity, CPM just one.
Differences aside, both PERT and CPM analyze the following components:
List of required tasks
Estimated duration for each task
The two techniques can be used in tandem to boost their effectiveness. You can use PERT to get more realistic estimates of task durations before proceeding to calculate the critical path and floats.
Critical path method vs. Gantt chart
Gantt charts are horizontal bar charts that map out project activities, which can be tracked against a set timeline. Both CPM and Gantt charts show the dependencies between tasks.
Let’s go over some differences between the two tools:
Visualizes critical and non-critical paths and calculates project duration
Displayed as network diagram with linked boxes
Doesn’t show resources required
Plots activities on network diagram without timescale
Visualizes how project activities are progressing
Displayed as horizontal bar chart
Shows resources required for each activity
Plots activities on a timescale
Gantt charts can be paired with CPM to track critical paths over time to keep your project running on schedule.
Use critical path for better project management
CPM can be a useful asset in project management, particularly for planning tasks and managing resources. With the help of project planning tools, you’ll be able to create schedules and track projects with ease. To further increase your work efficiency, check out 12 tips to be more productive today.