Z Score Calculator
Find how unusual a value is with the z-score. Enter your value (x), the mean and the standard deviation to get the z-score, its percentile from the normal table, and the percentage of data above and below it.
Enter values — the result will show here live.
How to use
- Enter your value (x), the mean of the data set, and its standard deviation.
- The result appears live: the z-score, the percentile, and the percent area above this value.
- A positive z-score means your value is above the mean; a negative one means it is below.
- The calculation assumes a normal distribution — check that your data fits before using the result.
Note: Formula: z = (x - mean) / SD. The percentile is taken from the standard normal table (cumulative) — if z is positive the value is above the mean, if negative it is below. This calculation assumes a normal distribution.