What Is the Critical Path in Project Management?


An illustration shows two project managers determining the critical path in project management by laying out all the tasks in their job from start to finish.

If you have ever estimated how long it will take to finish a project—say, putting together a bake sale for your kids’ school—then you have created a critical path. A rough critical path, but a critical path nonetheless.

The critical path in project management, which is a key tenet of project management theory, is the order of scheduled tasks that determines the duration of the project. In our bake sale example, it might include buying ingredients, baking cookies and brownies, boxing up the treats, setting up tables and determining prices.

Critical path analysis is used in numerous fields, from construction and engineering to software development and research. Basically, any project with interdependent elements can benefit from critical path analysis.

How Do You Calculate the Critical Path?

If you’re new to a field or a certain type of project within your field, determining completion length can be daunting. Never fear, though. Experts are almost always happy to share their experience-informed advice. And it never hurts to make some lists:

  1. First, jot down every task that needs to be completed, beginning to end.
  2. Calculate the duration of each task. This is when you will want to tap your network for reliable estimates.
  3. Take note of task dependencies. That means marking all the tasks that can’t be started unless the ones before it are finished. You can’t put a roof on a house unless the walls are up. But you can begin sewing a wedding veil before the dress is complete—so that’s not a dependency.
  4. Create a list of milestones or major phases. This technique can help keep you on track. Ingredients for bake sale purchased? Check. Cupcakes out of the oven? Check. Price tags written and signage secured? Check and check.

What is ‘Float’ in Project Management?

To determine when you must start a project in order to meet the deadline, calculate the duration and subtract it from the latest possible finish date—your final, no-excuses deadline. That gives you your latest start date. On the flip side, to figure out the earliest possible finish, add the project duration to the earliest date you are able to start.

Subtract the latest finish from the earliest finish and you have your “total float,” or the wiggle room available to delay any particular task without upsetting your project schedule. There is also “free float,” or the window you have to complete an individual task without it upsetting the next task that needs to be done.

Be aware, though, that a wrench in any individual task can throw off the entire project schedule. If the grocery store is out of flour, for example, making cookies for the bake sale will be delayed until you can get to another store. Unless you are willing to shuffle. Maybe you flip the order of what you are making and stick with Rice Krispies treats until you can get some flour. Maybe you ask someone else to bake with you to make up for lost time.

You can never anticipate every wrinkle that might come up during your project, but thinking through possible solutions can help you navigate whatever pops up. Maybe you’ll have to allocate additional resources or run certain tasks simultaneously.

The bottom line: A critical path is not static. It can be changed, and often must be.

A critical path lets you see where your efforts cannot be compromised and how your efficiencies can be maximized, ultimately leading to happy customers and repeat business.

Earn Your Master of Project Management Degree

At Elmhurst University, we help you develop a set of core competencies, including how to calculate the critical path in project management, so you can deliver projects on time, on budget and to specification—in a wide range of fields and occupations. Learn more about our Master of Project Management degree and learn to lead in a collaborative world.

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