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Project Estimation Calculator

Estimate project duration and cost using three-point estimation.

About Project Estimation Calculator

The PERT weighting produces an expected value above the most likely estimate whenever the pessimistic tail is longer than the optimistic one, which it almost always is. Quoting at 85 per cent confidence adds roughly one standard deviation. Quoting the most likely estimate means missing the deadline about half the time, which is why commercial quotes are made at a stated confidence level instead.

Formula

Project Estimation

PERT expected = (optimistic + 4 × most likely + pessimistic) ÷ 6

PERT
Weights the most likely estimate four times the extremes
standard deviation
The optimistic to pessimistic range divided by six

Worked example

With the default values below, Project Estimation Calculator returns PERT Expected Hours of 126.67. Change any input above and every figure here is recalculated in your browser.

Inputs used

Optimistic estimateminimum 0 h
80 h
Most likely estimateminimum 0 h
120 h
Pessimistic estimateminimum 0 h
200 h
Hourly rateminimum 0
85
Confidence levelone of 50 per cent, 85 per cent, 95 per cent
85 per cent

Results

PERT Expected Hours
126.67 h
Standard Deviation
20.000 h
Hours at the Chosen Confidence Level
147.39 h
Cost at That Confidence Level
$12,527.87
Contingency Above the Expected Estimate
20.72 h

Step by step

  1. 1Values used
  2. 2Project Estimation
  3. 3PERT Expected Hours= 126.67 h
  4. 4Standard Deviation= 20.000 h
  5. 5Hours at the Chosen Confidence Level= 147.39 h
  6. 6Cost at That Confidence Level= 12,527.87
  7. 7Contingency Above the Expected Estimate= 20.72 h

Assumptions and limits

  • The result is derived only from the 5 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 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • This is an estimate for general information and not professional financial, tax or legal advice. See the full disclaimer for the limits that apply to this kind of calculator.

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

Frequently Asked Questions

How is Project Estimation calculated?

PERT expected = (optimistic + 4 × most likely + pessimistic) ÷ 6 The PERT weighting produces an expected value above the most likely estimate whenever the pessimistic tail is longer than the optimistic one, which it almost always is. Quoting at 85 per cent confidence adds roughly one standard deviation.

Why does Project Estimation matter?

Quoting the most likely estimate means missing the deadline about half the time, which is why commercial quotes are made at a stated confidence level instead.

What values do I need to enter?

This calculator takes 5 inputs: Optimistic estimate, Most likely estimate, Pessimistic estimate, Hourly rate, Confidence level. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

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