Critical chain project management (CCPM)
Also: Critical chain, Project buffer, Feeding buffer
Quick definition: A scheduling and control method, based on the theory of constraints, that removes safety time from individual task estimates and pools it into shared buffers, then manages the project by monitoring how fast those buffers are consumed.
Explanation
Beginner explanation
Instead of padding every task "just in case", CCPM schedules each task at a realistic, tight duration and puts the spare time together at the end of the chain. Managers then watch how much of that spare time gets used up.
Technical explanation
Developed by Eliyahu M. Goldratt and introduced in his 1997 book Critical Chain, CCPM schedules tasks at roughly 50% ("best guess") durations and moves the removed safety into buffers placed strategically: a project buffer at the end of the critical chain (its end is the committed delivery date), feeding buffers where non-critical paths join the critical chain, and resource buffers that alert key resources ahead of need. Unlike the Critical path method, the critical chain accounts for resource dependencies as well as logical ones. Buffer sizes are fixed once the project starts, and progress is controlled through buffer consumption rather than individual task dates.
Practical example
A modular-housing manufacturer reschedules factory production of 40 units using CCPM. Task estimates drop from padded durations to 50% estimates, and the saved time forms a 12-day project buffer. Weekly reviews focus on buffer consumption instead of whether each module station hit its date.
Why it matters
Padded task estimates tend to be used up regardless of need (work expands to fill the time). Pooling safety in visible buffers protects the delivery date and focuses attention where delays actually threaten it.
Common confusion
CCPM is not the same as the Critical path method: CPM manages task dates and float; CCPM manages shared buffers and explicitly considers resource contention.
Standards and references
- Critical chain project management. Wikipedia.Widely accepted professional interpretation
Supports: Origin in Goldratt's 1997 book; 50% estimates; project, feeding and resource buffers; buffer sizes locked; buffer management and fever chart - Critical chain monitoring (product documentation). Sciforma.Widely accepted professional interpretation
Supports: Critical chain monitoring by buffer consumption rather than task dates
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VDC Stack.io. (2026). Critical chain project management (CCPM). In VDC Stack.io Knowledge Dictionary. Retrieved from https://vdcstack.io/dictionary/critical-chain-project-management/