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Critical Path Duration Calculator

Work out critical path duration instantly with clear inputs, formula shown and shareable results.

About Critical Path Duration Calculator

The critical path is the longest chain through the network and it sets the project duration. Equally important is the float on near-critical paths: a path with only a few days of float will become critical as soon as it slips, which is where most schedule surprises originate.

Formulas

Critical path

Project duration = Longest path duration

Total float

Float on a path = Critical path duration - Path duration

Worked example

With the default values below, Critical Path Duration Calculator returns Critical path duration of 56.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Path 1 duration
42 days
Path 2 duration
56 days
Path 3 duration
49 days
Path 4 duration
38 days

Results

Critical path duration
56.0
Next longest path
49.0
Float on the next longest path
7.0
Smallest non-zero float
7.0

Step by step

  1. 1Values used
  2. 2Critical path
  3. 3Total float
  4. 4Critical path duration= 56.0
  5. 5Next longest path= 49.0
  6. 6Float on the next longest path= 7.0
  7. 7Smallest non-zero float= 7.0

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, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 1 decimal place, 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

Can there be more than one critical path?

Yes, and it is common in well-optimised schedules. Multiple critical paths mean multiple simultaneous sources of delay risk.

Why watch near-critical paths?

Because compressing the critical path simply makes the next longest path critical. Schedule improvement is iterative for exactly this reason.

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