The Easy Guide to the Critical Path Method

New project managers are expected to hit the ground running. Not only are they responsible for their own work, but for that of their project team as well. Understanding the Critical Path Method is a vital step towards successfully planning and scheduling the tasks of the team.

What is CPM?

The CPM (Critical Path Method) is a mathematical approach to scheduling a set of project activities. It enables you to assess task priority, the resources required and possible shortcuts to project completion.

CPM is based on the creation of a sequence of dependent tasks (i.e. tasks that can only be performed after earlier tasks are complete). Performing Critical Path Analysis on this sequence allows you to work out possible parallel sequences (i.e. tasks that can be performed simultaneously). The Critical Path is the longest chain of dependent tasks required for project success. A key tool for the creation of a Critical Path is the MS Project Gantt Chart capability, which provides a visual representation of task dependencies, task priorities and the interaction of critical paths across multiple projects.

How much does it cost?

CPM is free to use. You can apply it to your project simply by following six simple steps.

Training in the Critical Path Method is included in most introductory project management training courses. Critical Path Method training-courses are an essential way of formalising knowledge learnt on the job, and ensure that project managers correctly implement the Critical Path Method. Critical Path Analysis software, such as MS Project, enables project managers to evaluate the data thoroughly and accurately.

Six Simple Steps

1. Specify the individual tasks necessary for project success

For example:

Project Goal - prepare a perfect breakfast-in-bed on Mother's Day

Necessary Tasks:

• Fry the eggs and bacon
• Heat up the baked beans
• Buy a Sunday newspaper
• Buy flowers
• Make the hash browns
• Find a recipe for the hash browns
• Buy the ingredients
• Make a shopping list
• Make a pot of coffee
• Cook the tomatoes and mushrooms
• Find a vase
• Put flowers in the vase

1. Determine sequences of tasks

If I try to do the tasks in the order that they occur to me (see above) then my project will result in a mess of broken eggs and burnt coffee! Before embarking on my project I need to put the tasks into their logical order and priority.

2. Draw network diagram

A CPM network diagram illustrates the dependency relationships between each tasks. I cannot fry the eggs and the bacon until I have bought the ingredients. I cannot make a shopping list until I have found a recipe.

3. Identify the critical path (the longest chain of dependent tasks)

For example:

Find a recipe for hash browns > Make a shopping list > Buy ingredients > Make hash browns

4. Estimate completion time

I need to work out how long each task will take me.

By adding up the estimated completion time for each activity in the longest chain of dependent tasks, I will be able to work out the maximum duration of the project.

5. Update for progress

I might have estimated that finding a vase would only take me five minutes. If I discover that all of our vases are broken then I have to either increase my schedule and budget to allow for the purchase of a new vase, or come up with an alternative solution (like a tall glass or a jug) or reduce the scope of the project and go without the flowers.

Updating for progress is a vital part of the CPM, as it ensures that expected project duration and outcomes remain viable. Even more essential, however, is risk assessment. If I had taken into account the possibility that there might not be any vases then I might have found a solution earlier on.

The Critical Path Method enables project managers to work out the most efficient task route, task priorities and the most effective ways of shortening project duration. By understanding which activities lie on the Critical Path and then monitoring their progress, the project manager can help to deliver the project on time. Any delays to these critical tasks will delay the project completion. This is why the Critical Path Method remains one of the most important tools for any project manager.

If you need to learn more about CPM and other project management techniques, then you might be interested in our Introduction to Project Management training courses. To find out more about fundamental Critical Path software tools, then please visit our MS Project course page.