Z-Score Calculator
Enter the value, mean and standard deviation.
Result
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Enter numbers to see the result.
Percentile (approx)
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Within 1 sigma?
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Formula: z = (x - mu) / sigma. About 68% of normal data falls within z = +/-1, 95% within +/-1.96.
Compute the z-score of a value: how many standard deviations it sits from the mean.
Enter the value, mean and standard deviation.
Enter numbers to see the result.
A z-score subtracts the mean and divides by the standard deviation, converting any measurement into units of sigma. A score of 115 on a test with mean 100 and sigma 15 becomes z = +1.0: exactly one standard deviation above average.
For roughly normal data, the z-score maps to a percentile through the standard normal curve: z = 1.0 beats about 84% of values, z = 1.96 marks the top 2.5%. The tool estimates this percentile for every result.