Three Point Estimate Calculator

Work out three point estimate instantly with clear inputs, formula shown and shareable results.

About Three Point Estimate Calculator

Three-point estimating can use a triangular distribution, which weights all three points equally, or a beta distribution, which weights the most likely case four times. Triangular is more conservative when the worst case is far from the mode, so comparing both reveals how much the choice matters.

Formulas

Triangular mean

Triangular = (Best + Most likely + Worst) / 3

Beta (PERT) mean

Beta = (Best + 4 x Most likely + Worst) / 6

Worked example

With the default values below, Three Point Estimate Calculator returns Selected estimate of 130.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Best case: 80 hours
Most likely: 120 hours
Worst case: 220 hours
Distributionone of Beta (PERT, 1-4-1 weighting), Triangular (equal weighting): Beta (PERT, 1-4-1 weighting)

Results

Selected estimate: 130.00
Beta (PERT) estimate: 130.00
Triangular estimate: 140.00
Standard deviation: 23.333

Step by step

1Values used
2Triangular mean
3Beta (PERT) mean
4Selected estimate= 130.00
5Beta (PERT) estimate= 130.00
6Triangular estimate= 140.00
7Standard deviation= 23.333

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 3 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

Which distribution should I use?

Beta when you have reasonable confidence in the most likely value; triangular when the worst case is a genuine tail risk you do not want to under-weight.

What is the worst case supposed to represent?

A realistic bad outcome — roughly a 5% chance of being exceeded — not an absolute catastrophe. Including the catastrophe distorts both means.