Z-Score Calculator — Standard Score and Percentile Free

FREENo Sign-upInstant Results100% Browser-Based

Z-Score Calculator

Calculate the Z-score (standard score) and percentile rank for any value in a normally distributed dataset.

Raw Score (X)

Mean (μ)

Std Deviation (σ)

Z-Score Reference Table

All calculations run in your browser — nothing is sent or stored. Browse all free tools · Etsy Shop ↗

Frequently Asked Questions

What is a Z-score?

A Z-score measures how many standard deviations a value is from the mean. Z = (X − μ) ÷ σ. A Z-score of 1 means the value is 1 standard deviation above average. Used in statistics, standardized testing, finance, and quality control.

What Z-score is needed for a specific percentile?

Z = 1.645 for 95th percentile. Z = 1.96 for 97.5th (used in 95% confidence intervals). Z = 2.576 for 99.5th. Z = 0 for 50th percentile (the mean). Negative Z-scores are below the mean.