Z-Score Calculator
Quick answer: Enter a value, mean, and standard deviation to get the z-score and percentile.
A z-score tells you how many standard deviations a value is from the mean. Enter the value, population mean, and standard deviation to find the z-score and its corresponding percentile.
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Last reviewed: April 2026Report an error
Z-Score
0.50
Z-score: 0.50, percentile: 69.15%.
Z-Score
0.50
Percentile
69.15%
Standard Normal Distribution
68% of values fall within ±1 σ · 95% within ±2 σ · 99.7% within ±3 σ
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How to Use This Z-Score Calculator
- 1Enter the data value you want to analyze.
- 2Enter the population mean (average).
- 3Enter the standard deviation.
- 4Read the z-score and corresponding percentile.
Frequently Asked Questions
- A z-score of 1 means the value is exactly one standard deviation above the mean — at approximately the 84th percentile.
- Z-scores between -2 and +2 are considered normal. About 95% of data falls within ±2 standard deviations from the mean.
- Z-scores are used in standardized testing (SAT, GRE), quality control, medical reference ranges, and financial risk analysis.
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