Critical Path Method with Example  PDF

What is a Critical Path Method (CPM)?

→ The Critical Path Method is used to determine the shortest possible time to complete the project.

→ The CPM is a sequence of activities of a project's starting activity & time and the project's finish time and activity.

→ This tool is totally based on mathematical calculations and is used for scheduling project activities.

→ The CPM was developed by James E. Kelley and Morgan R. Walker in the 1950s.

→ Initially, the CPM_Method was used for managing plant maintenance projects.

→ CPM_method is used for planning and scheduling activity.

→ This_method also shows the interrelationship between the_time and cost of the_project.

→ Critical_Path_Method helps us to assess the different possibilities of project planning.

→ This method is one of the parts of the Arrow Diagram.

→ Refer to this article for fundamental of Arrow Diagram/Critical_Path_Method_Basics

👉 Download Critical Path Method with Example PDF File

Where CPM Method is used?

→ CPM_Method is used in the below fields

  • Software Development
  • Construction
  • Aerospace & Defence
  • Research Projects
  • Product Development and many more fields

Critical Path Method Example

→ Refer to the below example for understanding how to identify the critical path in project management.

→ We will follow the below five steps for understanding the CPM_Method.

→ For calculation, we will refer to the activity from A to K, completion time duration, and the immediate predecessors as mentioned in 1st step.

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What are the steps in CPM?

→ There are five steps in the CPM_Method as mentioned below.

  1. Step_1: List Out the Activity
  2. Step_2: Forward Pass Calculation
  3. Step_3: Backward Pass Calculation
  4. Step_4: Float Calculation for Each Activity
  5. Step_5: Identifying the Critical_Path

Step 1: List Out the Activity

→ First of all, we will list out all_activity, their immediate predecessors, and completion time.

→ For this refer to the below table.

Data for Construction of CPM

→ Now with the help of the above table, we will simplify and arrange all_activity and time with the critical path method.

→ In this example, A,B,C,D,E,F,G,H,I,J, and K are representing the activities.

Step 2: Forward Pass Calculation

→ In the forward pass, we calculate the Starting durations of all the activities.

→ So we can easily show the calculations from the below picture.

→ It starts from the first_activity and after that, we will add the time period as per the_activity.

→ By repeating this process we will get the final time of the end of all_activity with the different paths.

Forward Pass Calculation

Step 3: Backward Pass Calculation

→ Now, in the third step, we will calculate the backward pass.

→ In the backward pass calculation, we will take the end activities time as start_time as a finish_time.

→ In this example, it is 24.

→ The backward pass is processed by subtracting the duration of the activities leading to the end_activity node.

→ By repeating this process we will arrive at the finish_time which means at the beginning.

Backward Pass Calculation

Step 4: Float Calculation for Each Activity

→ Now the fourth step is to calculate the float of each_activity.

→ The float is the simple difference between the backward pass count and the forward pass count.

→ We can easily see the float value for all activities from the below picture.

Float Calculation

Step 5: Identifying the Critical_Path

→ Now the final step is to identify the critical_path out of all different possible paths.

→ The critical_path is the longest path in the network diagram.

→ The total float of the critical_path is zero.

→ It is shown as light red color in the below picture.

Critical Path Calculation

Advantages of CPM Method:

→ This tool is used for planning, scheduling, monitoring, and controlling various types of projects.

→ It helps us for proper communications between departments and functions.

→ We can estimate the expected project completion date.

→ This tool is very easy to use.

→ We can identify the critical path with the help of this tool.

→ It is very useful in monitoring costs

→ This tool is visually very effective so all people can easily understand.

→ We can also reduce the project completion timelines by using this method.

→ CPM Method improves the decision-making ability of the team.

→ By using this tool we can able  to determine which activities can be delayed without delaying the project

Disadvantages of CPM Method:

→ The reliability of this tool is based on accurate estimates and assumptions.

→ This tool does not give surety of the success of the project.

→ If we have many activities then our network diagram will also be complicated.

→ The estimate of activity timing is subjective and depends on the judgment.

Limitations of the Critical Path Method:

→ This method is not feasible for large and complex problems. We need to use software for this.

→ We can not able to allocate resources by this method.

→ If activity durations are determined wrong then the critical path of the project will be wrong.

→ If there are many other similar duration paths available in the project at that time it is very critical to identify the Critical Path of the project.

👉 See Also:


  1. Dear sir,
    Why does activity F ends in activity H? Would you mind clearing me please?

    1. Your doubt is already mentioned into the presentation your can read again I hope you will definitely find your solution.

  2. How can we use critical path on agile projects (Scrum Framework for instance)?

    1. You can refer above case study and apply step wise so you can easily use this method for your project.


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