Free Web Tool · PERT / PMBOK

PERT 3-Point Estimate

PERT Beta-distribution estimate from optimistic O, most likely M, and pessimistic P — gives expected duration TE = (O + 4M + P)/6, variance, and triangular alternative.

Input

Results

Beta TE = (O + 4M + P) / 6—
Std dev σ = (P − O) / 6—
Variance σ²—
Triangular TT = (O + M + P) / 3—
Confidence range TE ± k·σ—
Method

PERT (Beta) — TE = (O + 4M + P)/6, σ = (P − O)/6. For a single activity with normal-approx Beta, the 95% range is TE ± 1.96σ. Triangular distribution mean = (O + M + P)/3 (different model — useful as a sanity check).