Z-Score Calculator

Standardize a value against a normal distribution — z-score, percentile, and two-tail p.

Calculator Numbers & Math Updated Apr 20, 2026
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How to Use
  1. Enter a value, mean, and standard deviation.
  2. Percentile and tail probabilities update live.
Input
Result

Formulas

Z-score
z = (x − μ) / σ
Percentile
Φ(z) · Abramowitz & Stegun approximation

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