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.


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.

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