Critical Path and Why is it Important?

In my formative years as a business analyst, I was once summoned by my project manager into the war room while working on an eCommerce project for one of my company’s high profile clients. We were about 2 months away the launch date and the PM asked us for the critical path. My first question (to myself) was, “what in the world is a critical path and why is the PM asking me this.”

Here is how I interpreted that question, “well.. the project is critical to my organization, it is critical to succeed, so everything on this project is the critical path”.

I am on the other side now as a project manager; I have learned to respect the critical path. Now I think back to that situation and find it amusing that we were in the war room 2 months away from launch trying to discover the project’s critical path.

The critical path definition that I have come to recognize is, “Longest sequence of activities in a project plan which must be completed on time for the project to complete on due date. An activity on the critical path cannot be started until its predecessor activity is complete; if it is delayed for a day, the entire project will be delayed for a day unless the activity following the delayed activity is completed a day earlier.” [Definition from]

The other method of looking at the critical path is to determine which activities have absolutely no float. Float is defined as the amount of time that an activity on your project can be delayed without causing a delay to the project end date. Here is a graphical representation of the critical path on a project with float:

Figure 1: Network Diagram

In this illustration (network diagram), my critical path is the activities marked in red. They total 12 days;  my end will be 12 days from when I start the project and any delay in Activity 1, 3 or 4 will delay the end date.  Therefore, I have no float in any of these activities.

In the same illustration, Activities 2 and 5 will consume 5 days and are not on the critical path because they have float built in them. I can delay either of these activities by at least 7 days without affecting the end date. Delays of more than 7 days will also change the critical path and then activities 2 and 5 will be the critical path of the project.

So you can see why it is important to constantly monitor your critical path and to ensure the end date does not change. If that end date does change, you have to determine the new critical path on your path and share this data with your client counterparts.

It would be literally impossible for a project manager to draw out a network diagram on a large project and to calculate the critical path. I have found Microsoft Project as a good tool for the type of software development and implementation projects I manage. I use this tool often to create a timeline and calculate the critical path as it gives me an easy to use interface to data in a graphical format that is very easy to interpret.

AMIT TRASI | Project Manager

Amit is responsible for institutionalizing project management governance at KTL to streamline ERP implementations. With over 15 years of technology experience as a software developer, project manager, and program manager, Amit has managed end-to-end ERP implementations with Dynamics NAV and GP as well as POS implementation with e-Commerce front end. He holds extensive experience deploying POS and ERP applications at non-profits, theme parks, and museums across the United States. Amit joined KTL in October of 2013 and holds an MBA in Information Systems as well as holding a Project Management Professional certificate.


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