![\"Critical](\"https:\/\/plaky.com\/learn\/wp-content\/uploads\/2023\/04\/Critical-path-method-project-management-social.png\")
<\/figure>\n<\/div>\n\n\n- \n
- The critical path method (CPM) is a tool used in the planning phase to determine the project\u2019s approximate length.<\/li>\n\n\n\n
- Finding the project\u2019s critical path includes identifying activities, their duration, and their interconnections before drawing a diagram and discovering the critical and non-critical paths.<\/li>\n\n\n\n
- One of the best and most efficient ways to map out a project\u2019s schedule and total duration is to calculate the critical path.<\/li>\n\n\n\n
- The CPM and Gantt charts are both visual tools in project management. The former uses diagrams to represent project activities while the latter uses a horizontal timeline.<\/li>\n<\/ul>\n\n\n\n
What is the critical path method (CPM)?<\/h2>\n\n\n\n
The critical path method is a scheduling algorithm that calculates how long a project will take to complete by identifying its critical path.<\/strong><\/p>\n\n\n\n
The critical path is the longest sequence of dependent project activities<\/a>. CPM also highlights how much extra time you have to perform activities that aren\u2019t on the critical path, thereby showing you where you can be flexible without missing the deadline. <\/p>\n\n\n\n
This allows you to prioritize tasks and manage resources in a way that supports progress toward project completion.<\/p>\n\n\n\n
\n
\n\nFree project management software<\/h2>\n
Looking for a tool that will help you manage and complete projects successfully? Try Plaky by CAKE.com for free!<\/p>\n\n
\n Try for free<\/a>\n\n Download<\/a>\n <\/div>\n <\/div>\n\n\n\n \n ![\"Illustration\"](\"https:\/\/plaky.com\/learn\/wp-content\/themes\/cake-learn\/src\/images\/plaky\/banners\/features.png\")
\n <\/picture>\n <\/div>\n<\/div>\n <\/p>\n\n\n\nHow to find a project\u2019s critical path<\/h2>\n\n\n\n
Finding a project\u2019s critical path requires a thorough understanding of the project\u2019s activities and the necessary effort to complete them.<\/p>\n\n\n\n
Here are the 6 steps to find the project\u2019s critical path:<\/p>\n\n\n\n
- \n
- List project activities.<\/li>\n\n\n\n
- Identify the dependencies.<\/li>\n\n\n\n
- Create a network diagram.<\/li>\n\n\n\n
- Estimate the duration of tasks.<\/li>\n\n\n\n
- Calculate the critical path.<\/li>\n\n\n\n
- Calculate the float.<\/li>\n<\/ol>\n\n\n\n
Let\u2019s go through the critical path method in detail.<\/p>\n\n\n\n
Step #1 List project activities<\/h3>\n\n\n\n
You can use a work breakdown structure<\/a> to list all the project activities hierarchically. This means you\u2019ll divide the project into logical units that you will then decompose further into specific tasks.<\/p>\n\n\n\n
The WBS usually takes the form of a tree diagram, but you can also create grouped task lists<\/a>.<\/p>\n\n\n
\n![\"Example](\"https:\/\/plaky.com\/learn\/wp-content\/uploads\/2023\/04\/Example-of-a-work-breakdown-structure.png\")
Example of a work breakdown structure<\/figcaption><\/figure>\n<\/div>\n\n\n Step #2 Identify dependencies<\/h3>\n\n\n\n
Once you\u2019ve listed all the activities necessary to achieve project goals, you can start connecting them. You\u2019ll know if there are task dependencies<\/a> if, for example, a task can\u2019t start before another is finished.<\/p>\n\n\n
\n![\"Task](\"https:\/\/plaky.com\/learn\/wp-content\/uploads\/2023\/04\/Task-dependencies-in-project-management.png\")
Task dependencies in project management<\/figcaption><\/figure>\n<\/div>\n\n\n Step #3 Create a network diagram<\/h3>\n\n\n\n
A project network diagram<\/a> is made of nodes and arrows that represent activities, their relationships, and their durations.<\/p>\n\n\n\n
For now, you can draw the diagram and add the time estimates in the next step.<\/p>\n\n\n
\n![\"Example](\"https:\/\/plaky.com\/learn\/wp-content\/uploads\/2023\/04\/Example-of-a-project-network-diagram.png\")
Example of a project network diagram<\/figcaption><\/figure>\n<\/div>\n\n\n Step #4 Estimate the task duration<\/h3>\n\n\n\n
Now, it\u2019s time to write down the estimated duration of each task. <\/p>\n\n\n\n
The most common way to make estimates is to rely on previous experiences. If you don\u2019t know how long an activity will take, you can resort to expert judgment, group decision-making, or yet another estimation technique.<\/p>\n\n\n\n
In this step, you can also use the forward and backward pass technique<\/strong>:<\/p>\n\n\n\n
- \n
- The forward pass is the act of calculating the early start (ES) and early finish (EF) times of all activities and highlighting the critical path.<\/strong> Early start time is the earliest possible point at which you can start working on a task while early finish time refers to the earliest moment at which it is possible to finish a task.<\/li>\n\n\n\n
- The backward pass is the act of calculating the late start (LS) and late finish (LF) times of all project activities.<\/strong> Late start time denotes the latest point at which you can start work on an activity without it prolonging the overall project timeline<\/a>. On the other hand, late finish time is the latest point at which you can complete an activity without it extending the overall timeline.<\/li>\n<\/ul>\n\n\n\n
First, you\u2019ll need to calculate the ES and EF to determine the forward pass.<\/p>\n\n\n\n
The ES for the first task(s) in a project is set to 0.<\/p>\n\n\n\n
To calculate the ES for all other tasks, just copy the EF (early finish time) of the preceding dependent task. If a task is dependent on 2 or more previous activities, refer to the activity with the longer ES.<\/p>\n\n\n\n
To calculate the early finish time for a task, you take its ES and add the task duration (Dur).<\/p>\n\n\n\n
EF = ES + Dur<\/p>\n\n\n\n
Since the first activity in a project generally has an ES of 0, the EF will be identical to the duration of the first activity.<\/p>\n\n\n\n
All dependent tasks that follow immediately after it will take the first task\u2019s EF as their ES. Add their duration to it to calculate their EF. <\/p>\n\n\n\n
Once you\u2019ve finished calculating the forward pass to identify the critical path, it\u2019s time to do a backward pass using late start and late finish values.<\/p>\n\n\n\n
To calculate the LS of an activity, use the following formula:<\/p>\n\n\n\n
LS = LF \u2013 Dur<\/p>\n\n\n\n
The LF of a node is equal to the LS of the subsequent one. <\/p>\n\n\n\n
Tasks that are on the critical path have identical LF and EF values.<\/p>\n\n\n\n
To calculate the LF of tasks that aren\u2019t on the critical path, you have to start with the project completion node and work your way backward.<\/p>\n\n\n\n
Step #5 Calculate the critical path<\/h3>\n\n\n\n
The critical path is the sequence of dependent activities with the longest overall duration<\/strong>.<\/p>\n\n\n
\n![\"Example](\"https:\/\/plaky.com\/learn\/wp-content\/uploads\/2025\/03\/critical-chain-PM-1.png\")
Example of the Critical Path Method diagram<\/figcaption><\/figure>\n<\/div>\n\n\n In the diagram above, the C1-C2-C3 string of activities constitutes the critical path, as they take 30 days to complete.<\/p>\n\n\n\n
The alternative routes \u2014 consisting of activities A1-A2-A3 OR B1-B2-B3 \u2014 take only 27 days and 12 days to complete respectively.<\/p>\n\n\n\n
In other words, no matter how quickly you go through these secondary routes, the project won\u2019t be completed until the activities on the critical path are done. Even if activities B1, B2, and B3 took twice as long to complete, they wouldn\u2019t impact the deadline at all.<\/p>\n\n\n\n
Step #6 Calculate the float<\/h3>\n\n\n\n
Total float is the amount of wiggle room you have before you must start working on tasks that are not on the critical path<\/strong>.<\/p>\n\n\n\n
To calculate total float<\/a>, use either of the following formulas:<\/p>\n\n\n\n
\n\nTF = LF \u2013 EF<\/p>\n\n\n\n
TF = LS \u2013 ES<\/p>\n<\/div><\/div>\n<\/div><\/div>\n\n\n\n
Total float vs. free float<\/h4>\n\n\n\n
Total float is the total amount of extra time you have to complete tasks that are not on the critical path.<\/strong><\/p>\n\n\n\n
On the other hand, free float shows the extra time at disposal to complete a non-critical path task without delaying any subsequent tasks.<\/strong><\/p>\n\n\n\n
As you can see, the difference between them is entirely contextual.<\/p>\n\n\n\n
When we have several non-critical path tasks chained together, the backward pass calculations show that they all have the same float.<\/p>\n\n\n\n
But if you extend one of those tasks by any amount, you\u2019ll reduce the remaining float of subsequent tasks in that chain.<\/p>\n\n\n\n
However, you\u2019ll sometimes run into non-critical path tasks that aren\u2019t part of an expanded chain of such tasks. We say that those tasks have free float because using up their float won\u2019t reduce the float of any subsequent activity.<\/p>\n\n\n\n
For example, if we had just one task labeled A instead of the task chain A1-A2-A3, then A would have free float.<\/p>\n\n\n\n
\n\ud83d\udca1 Plaky Pro Tip<\/strong><\/p>\n\n\n\n
CPM is one of the most used techniques in project management. Check out some other popular project management tools here:<\/p>\n\n\n\n
- \n
- 10 Essential Project Management Techniques and How to Use Them<\/a><\/li>\n\n\n\n
- What Is Kanban Project Management?<\/a><\/li>\n\n\n\n
- Scrum in Project Management: An Overview<\/a><\/li>\n<\/ul>\n<\/div><\/div>\n\n\n\n
Critical path method example + template<\/h2>\n\n\n\n
Let\u2019s go through the critical path method step by step, using a YouTube video production project as an example.<\/p>\n\n\n\n
To make our YouTube video, we\u2019ll need a simple WBS like this:<\/p>\n\n\n\n
- What Is Kanban Project Management?<\/a><\/li>\n\n\n\n
- The backward pass is the act of calculating the late start (LS) and late finish (LF) times of all project activities.<\/strong> Late start time denotes the latest point at which you can start work on an activity without it prolonging the overall project timeline<\/a>. On the other hand, late finish time is the latest point at which you can complete an activity without it extending the overall timeline.<\/li>\n<\/ul>\n\n\n\n
- The forward pass is the act of calculating the early start (ES) and early finish (EF) times of all activities and highlighting the critical path.<\/strong> Early start time is the earliest possible point at which you can start working on a task while early finish time refers to the earliest moment at which it is possible to finish a task.<\/li>\n\n\n\n
![\"Illustration\"](\"https:\/\/plaky.com\/learn\/wp-content\/themes\/cake-learn\/src\/images\/plaky\/banners\/features@2x.png)
\n <\/picture>\n <\/div>\n<\/div>\n <\/p>\n\n\n\n![\"Map](\"https:\/\/plaky.com\/learn\/wp-content\/uploads\/2025\/03\/Activity-Node-1.png\")
![\"Example](\"https:\/\/plaky.com\/learn\/wp-content\/uploads\/2025\/03\/CPM-diagram-FLOAT.png\")
![\"Illustration\"](\"https:\/\/plaky.com\/learn\/wp-content\/themes\/cake-learn\/src\/images\/plaky\/banners\/default@2x.png)
\n <\/picture>\n <\/div>\n<\/div>\n <\/p>\n\n\n\n![\"Gantt](\"https:\/\/plaky.com\/learn\/wp-content\/uploads\/2023\/04\/Creating-a-project-schedule-in-a-Plaky-Gantt-chart.png\")
![\"CRM](\"https:\/\/plaky.com\/learn\/wp-content\/uploads\/2023\/04\/Organizing-tasks-and-their-start-and-due-dates-in-Plaky.png\")