Difference Between Critical Chain and Critical Path Project Management

Critical path and critical chain project management both look at what tasks need to be accomplished to complete a project, and in what sequence they need to be done. But they take different pathways to help project managers complete projects. 

According to A Guide to the Project Management Body of Knowledge (PMBOK® Guide), Seventh Edition, critical path project management (CPPM) looks at projects from the perspective of tasks. The critical path is the longest distance between a project’s start and its finish, including all tasks associated with it. CPPM describes the critical path of a project by estimating the time it takes for each task and the slack time between one task and the next task. The PMBOK® Guide also notes that “the Critical Path Method is used to estimate the minimum project duration and determine the amount of schedule flexibility on the logical network paths within the schedule model.”

Critical chain project management (CCPM) looks at a project from the perspective of resources. It calls for treating a project much like a relay race, with each task being completed as quickly as possible and then passed on to the next person. It puts the emphasis on the end goal rather than each individual assignment and ensures that resources are always available for each critical task. 

Critical path essentially looks at the length of a project based on task estimates from the people involved. Critical chain operates with the central idea that tasks do not take as long as people expect them to and attempts to plan accordingly.

The Critical Path Approach

The tasks on the critical path are “critical” because if any of them are delayed, the entire project is delayed. Resources are made available and time is estimated for each task, including the possibilities of an early or late start, and an early or late finish. By laying out this critical path, one after another, a project manager can create the longest potential distance for the project. 

Unlike critical chain project management, critical path allows for multitasking, which means two tasks on the critical path can be done simultaneously. Also, every task comes with an estimated buffer of time between each task. 

Changing Estimates

Another key difference is that critical chain project management challenges the time estimates for tasks in the critical path model.

Critical chain takes into account that given a week to do a task, a person might not start in earnest until later in the week (the “student syndrome”) or finish before the deadline but keep tinkering with the task (known as “gold plating”). 

Gold plating goes outside the scope of what was originally called for, but some project team members will do it anyways, according to the course. They feel it is the right thing to do, since they finished early. Critical chain would call for the individual to pass the project to the next person early, rather than gold plating their own task.

One way to manage gold plating is to take the original time estimate and then cut it in half. So, a 24-hour project (three workdays) is cut down to 12 hours, or a day and a half. The other 12 hours are put into a “project buffer” bucket of time that is added to the end of the project and may or may not be needed.

In short, extra time is stripped out of each task. People are asked to complete tasks as fast as possible with the highest amount of quality possible. They do not work toward a due date. They work to get it done as fast as possible. The project buffer time can then be used to make any adjustments that are needed.

Other Differences

In critical chain project management, those who have a task to complete are not given other work until their task is completed. They are not working toward a deadline. They are working toward completing their tasks as fast as possible while still retaining the quality of their work. Also, the project buffer time is put at the end of the project and used if needed. There is no time buffer between each task.

Critical path project management is typically most useful when resources may be an issue, and project managers must focus team members on certain critical tasks. Project leaders might prefer to use the critical path project management approach for a deployment project. Conversely, critical chain project management may be more useful when resources are not likely to be an issue and each task is hindered only by the time it takes to get the task completed.

PMBOK is a registered mark of the Project Management Institute, Inc.