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Project Timeline Calculator

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

About Project Timeline Calculator

Adding working days to a start date skips weekends, so 45 working days from 2 February 2026 lands in early April rather than mid-March. A 15% contingency raises the estimate to 52 working days - about 10.4 working weeks. Contingency should be held centrally rather than distributed into task estimates, where it disappears.

Formulas

Duration with contingency

days = base working days x (1 + contingency)

End date

add working days to the start, skipping weekends

Worked example

With the default values below, Project Timeline Calculator returns Working Days Including Contingency of 52. Change any input above and every figure here is recalculated in your browser.

Inputs used

Project start
2026-02-02
Duration in working daysaccepts 0–100,000
45
Contingency allowanceaccepts 0–1,000 %
15 %

Results

Working Days Including Contingency
52 days
Planned End Date
2026-04-06
End Date With Contingency
2026-04-15
Duration In Working Weeks
10.40

Step by step

  1. 1Values used
  2. 2Duration with contingency
  3. 3End date
  4. 4Working Days Including Contingency= 52 days
  5. 5Planned End Date= 2026-04-06
  6. 6End Date With Contingency= 2026-04-15
  7. 7Duration In Working Weeks= 10.40

Assumptions and limits

  • The result is derived only from the 3 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 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 hold contingency centrally?

Because contingency embedded in each task gets consumed by Parkinson's law. A central buffer is only drawn on when something actually slips.

Are public holidays included?

No, only weekends are skipped. Add the holiday count to the duration or subtract it from available days separately.

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