How to use it
- Enter the observed value and the data-set mean.
- Enter a positive standard deviation.
- Calculate and use the sign to see whether the value is above or below the mean.
Z-Score Calculator
Standardize a value relative to a mean and standard deviation.
About the Z-Score Calculator
A Z-score expresses an observation on a common scale by measuring its distance from the mean in standard deviations.
Z-score formula
Z = (value - mean) / standard deviation. A positive result is above the mean, a negative result is below it, and zero is exactly at the mean.
When it is useful
Standard scores help compare observations measured on different distributions, such as test results from classes with different averages and spreads.
Example
A score of 85 in a distribution with mean 75 and standard deviation 5 has a Z-score of 2, meaning it is two standard deviations above the mean.