Construction Scheduling: Critical Path Method (CPM)
Learn how to develop project schedules using CPM, calculate float, and identify the critical path.
Construction Scheduling: Critical Path Method (CPM) — Quick Overview
Get a quick, plain-language overview of this topic.
What is CPM?
The Critical Path Method (CPM) is a scheduling technique used to plan, organize, and control project activities.
Key Terms
| Term | Definition | |------|------------| | Activity | A task with duration and resources | | Critical Path | Longest path through the network | | Float (Slack) | Time an activity can be delayed without delaying the project | | Early Start (ES) | Earliest an activity can begin | | Late Finish (LF) | Latest an activity can finish without delays |
Forward Pass — Calculating ES and EF
- Start at Activity 1, ES = 0
- EF = ES + Duration
- For successors: ES = max(EF of all predecessors)
Backward Pass — Calculating LS and LF
- Start at last activity, LF = Project duration
- LS = LF - Duration
- For predecessors: LF = min(LS of all successors)
Float Calculation
Total Float = LS - ES = LF - EF
Activities with zero float are on the Critical Path.
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