Calculate normal distribution probability

Find the cumulative probability below a z-score or raw value.

JavaScript is required for live calculation.

You can still read how Calculate normal distribution probability works, the formula, examples, and FAQs below.

Inputs

Input mode

Z-score

Value x

Mean μ

Standard deviation σ

Results update when you click Calculate.

P(Z ≤ z)

97.50%

z = 1.9600 → cumulative area ≈ 97.50%

P(Z > z)

2.50%

Z-score used

1.9600

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Find the cumulative probability below a z-score or raw value. Uses the standard normal CDF approximation for P(Z ≤ z).

Uses the standard normal CDF approximation for P(Z ≤ z).

z = 1.96 → about 97.5% below (one-tailed).

Two-tailed?+

Double the upper-tail probability for symmetric two-tailed tests.