How to find the critical path in Project Schedule

Lets learn how to find the critical path in a project….

 
 

The Critical Path is the path with the longest duration in a project. In this article, I want to look at how you can find the critical path in Project Management. I have discussed  it in my previous article that the Critical path is that path that if you delay its activities, it will affect the finish date for the Project. Here I want to talk about the steps that you need to follow in order to calculate the Critical Path. Here the steps that you need to follow when you are calculating the critical path.
First step….



critical path calculation

determine the ES and EF from the beginning

The first thing you need to do is to determine the Earliest Start and Earliest Finish for each of the activities that you have in your project. In doing this based on what we have above, you need to use of 0 for the first activity Early Start date.


The next thing is to enter the first activity’s duration as its Earliest Finish date.
The next thing is to calculate the the Earliest Start for each successor activity using the latest EF from any of its predecessor activity plus or minus any leads or lags.
The next thing is to calculate the Earliest Finish date for each successor activity by adding its duration to the Earliest start date.
After that, you have to move through all the activities until you have an Earliest Start and Earliest Finish for each activity.


 

Second step……


BACKWARD PASS….
You need to enter the last activity’ s Earliest Start as its Late Finish time.
After you might have done that, you need to subtract the last activity’s duration from its Earliest Finish to determine what the Late Start for that activity will be.
The next thing is to calculate the Late Finish for each predecessor activity using the earliest Late Start from any of its successor activities plus or minus any leads or Lags.


The next thing is to calculate the Late Late Start for each predecessor activity by subtracting its duration from its Late Finish. If you are still confused m feel free to use our comment box.
The next thing is to move backward through all the activities until you have the Late Start and Late Finish for each of the boxes.

Calculating Float…..




I have talked about Float in one of my articles. Here now, if you want to calculate Float. Here are the procedures to follow…..

For each of the activities, subtract its Earliest Finish from its Late Finish to determine the Total Float for the Project.
Also, For each of the string of activities with float, calculate free float for the last activity in the string by subtracting its Earliest Finish from its successor activity Earliest Start.
The next thing is to identify the critical path as the path with the longest duration and Zero Float. So now look at your work and tell me which of the paths is the Critical Path.

Earlier in this article , I have talked about how to do crashing in Project schedule. Now I want to walk you through an example of how you can perform crashing for a Project. Follow me as we look at this together.


 

In the example given above, we have five activities , that is Activities A to E. We need to crash this project in a cost effective manner. If you are to be in my shoe which one of them will you advice me to crash. Before you leave you answer in the comment box. You have to take note of the normal cost and the crash cost for the project.

 

Before that we have a Formula for crashing the formula is:
Crash cost- normal cost/ normal time – crash time.


 

When you look at this table very well m you will discover that Activity D and C are the best candidate for crashing. Why do I choose that above other activities ?
  • Activity D has a net gain of three weeks at a cost of just $500 per week.
  • Activity C on the other hand reduces the schedule by two weeks at a cost of $1,500 per week.
  • Activity E is another possible candidate with a three week reduction at a cost of $2,000 per week.
  • The one you should not go near is Activity B which has a crash cost of $4,5000 per week and a reduction of only one week.
  • So if I will arrange any order for crashing, it will definitely be D, C,E,A and B which is the worst part of it.
 
Also, from what we have seen above, the total number of weeks by which the project could be shortened if all activities are on the critical part is 11. I got that by minus the normal time from the crash time. This will definitely cost us a whooping sum of  $23,000.
I do hope what I have explained is clear. If you have any further question, kindly make use of the comment box.


Action Point

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