Z-Score Calculator
Calculate a Z-score and its percentile from a value, mean and standard deviation.
A z-score tells you how many standard deviations a specific value is from the mean of its distribution — a standardized way to compare values across different datasets.
Why standardizing matters
A raw score alone doesn't tell you much without context — a z-score converts that raw value into a universal scale, letting you compare, for example, a test score against a national average, or a data point against an entire dataset's typical spread.
Frequently asked questions
What does a z-score of 0 mean?
It means the value is exactly equal to the mean of the distribution — no deviation in either direction.
What percentile does a z-score of 1.0 represent?
Roughly the 84th percentile in a normal distribution — about 84% of values fall below one standard deviation above the mean.