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Project Buffer Calculator

Work out project buffer instantly with clear inputs, formula shown and shareable results.

About Project Buffer Calculator

Critical chain scheduling removes the safety padding hidden inside individual task estimates and pools it into a single project buffer at the end, typically half the difference between safe and aggressive chain durations. Feeding buffers protect the critical chain from delays on merging paths.

Formulas

Cut-and-paste buffer

Project buffer = (Safe chain duration - Aggressive chain duration) / 2

Planned duration

Planned duration = Aggressive chain duration + Project buffer

Worked example

With the default values below, Project Buffer Calculator returns Project buffer of 30.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Critical chain duration with aggressive estimates
120
Critical chain duration with safe estimates
180
Longest feeding chain duration
40
Buffer as % of chain duration
50

Results

Project buffer
30.0
Planned duration including buffer
150.0
Feeding buffer for the longest feeding chain
10.0
Buffer as % of the critical chain
25.00%

Step by step

  1. 1Values used
  2. 2Cut-and-paste buffer
  3. 3Planned duration
  4. 4Project buffer= 30.0
  5. 5Planned duration including buffer= 150.0
  6. 6Feeding buffer for the longest feeding chain= 10.0
  7. 7Buffer as % of the critical chain= 25.00

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why pool the safety rather than leave it in tasks?

Because task-level padding is always consumed — Parkinson's law — while a shared buffer is only consumed by tasks that genuinely run late.

How is buffer consumption managed?

By tracking the percentage of buffer used against the percentage of chain completed. Consuming buffer faster than progress is the trigger for action.

Related Calculators

Project Buffer Calculator – Calculate Project buffer