Critical path vs. critical chain

Developed by Sophia Lykke Andersen

Abstract

In project management, keeping track of critical project activities is key to manage a schedule. This article attempts to clarify the difference between two well-established phenomena in project scheduling, which are often confused: critical path and critical chain. When activities have to finish before other can start, start before other can finish, or other relationships, paths of activity dependence form. The longest path of activities related to one another from start to finish of a project will be the most critical, as delays on this path will cause the whole project to be delayed. From this phenomenon rises the definition of the critical path. In real life, the critical path will only be the most critical considering all resources available at all times, people, materials, space, etc. As soon as resources are limited, other activities or paths of activities can become critical as well.
Allocating resources, considering additional constraints, and viewing the project schedule from a holistic point of view allows the manager to see chains of criticalities within the project. The critical chain will be the longest path of activities considering activity independence and resource constraints.
The article will take the reader through the history behind the methods, the methods of the two phenomena and provide an example in order to get a more hands-on understanding. Furthermore, a discussion of the principle differences between the two phenomena will be made, providing the reader with a better understanding of the limitations of each method and when what applies.
The article contains the following topics:
• Glossary
• History
• Critical path (Method, Example)
• Critical chain (Method, Example)
• Discussion (Differences, Limitations)

Core difference

A critical path identifies the longest path of activities to be finished in order to end the project .
A critical chain identifies the longest path of activities to be finished in order to end the project also considering resource constraints .