About the Z-Score Calculator
Converts between raw scores, z-scores, and percentiles, with a shaded standard normal bell curve.
What it is
Enter a raw value with a mean and standard deviation to compute its z-score, or enter a z-score directly to find the corresponding percentile and area under the standard normal curve.
Features
Both calculation directions
From raw value to z-score, or from z-score to percentile.
Shaded bell curve
Visualizes the selected region — left, right, two-tailed, or between −z and +z.
Step-by-step derivation
Shows the z-score formula substitution with your actual numbers.
Accurate normal CDF
Uses the Abramowitz-Stegun erf approximation, accurate to 4+ decimal places.