PERT and CPM are very similar in their approach but still present some differences.

CPM is used for projects that assume deterministic activity times; the times at which each activity will be carried out are known.

PERT, on the other hand, allows for stochastic activity times; the times at which each activity will be carried out are uncertain or varied.

Because of this core difference, CPM and PERT are used in different contexts. These mathematical techniques quickly spread into many private enterprises.