Critical Chain MethodCritical Path Method


CCPM vs CPM – Project scheduling is very important for bringing project costs and project time management kept under control and scrutiny. Project managers usually perform schedule network analysis once they are ready with the detailed list of resources, the work breakdown and effort estimates.

The Critical Path Method (CPM) as well as the Critical Chain Project Management (CCPM) are two popular techniques of schedule network analysis. These methods help project managers to analyze the project effectively and complete it in time.


CPM makes use of the concept of critical path for project scheduling. Critical path is the longest path in a network of tasks and it decides the shortest duration to complete the project. According to the Project Management Body Of Knowledge (PMBOK), any activity can be defined by four parameters:

  1. Early Start (ES)
  2. Early Finish (EF)
  3. Late Start (LS)
  4. Late Finish (LF)

Early Start and Early Finish are the earliest possible point in time an activity can start and finish respectively.
Similarly, Late Start and Late Finish are the latest possible point in time an activity can start and finish.
Most of the tasks have some amount of buffer added and it is known as Float. Float is the amount of time an activity can be delayed without affecting the project. There are two types of float:

  1. Total Float
  2. Free Float

Total Float is the amount of time a single task can be delayed without affecting the project completion and Free Float is the time a single task can be delayed without impacting the early start Early Start of any successor task. A project can have several critical paths and Total Float is zero on a critical path.

Critical Path Method is useful in project planning and control, risk reduction, cost-benefit analysis and efficient resource utilization. But CPM has some limitations as well. CPM does not focus much on non-critical tasks that can introduce risk later and also assumes low uncertainty in schedule dates. It uses buffer time less efficiently and does not consider resource dependencies. Moreover, critical path can change during project execution. Critical Chain Project Management (CCPM) plays a major role in overcoming these limitations.

CCPM technique modifies the project schedule to account for limited resources. It makes use of both deterministic as well as probabilistic approaches in scheduling whereas CPM uses only deterministic approach. Critical Chain Project Management benefits from the best practices of planning and control processes of PMBOK,

Theory of Constraints and also Reduce Variations by Six Sigma. CCPM considers resource constrained situations and optimum use of buffers. CCPM could successfully overcome phenomenon including Parkinson’s Law (work expands to fill the available time), Murphy’s law (what can go wrong will go wrong), Student Syndrome (people start to work in full fledge only while nearing deadline) and bad multitasking.

In case of CCPM, both critical and non-critical tasks are focused where the focus is only on critical tasks in case of CPM. Project duration can be reduced by 20% – 40% and resources can be more effectively utilized if you use CCPM technique. In short, CCPM can be considered as an improvement to CPM.

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