Z-Score Calculator
Enter a data value, the mean, and the standard deviation of its distribution to calculate its z-score.
Z-Score Calculator
Calculate a z-score (standard score) from a value, mean, and standard deviation.
This is a straightforward statistical calculation; it assumes the standard deviation entered accurately describes the relevant distribution.
A z-score standardizes a value relative to its distribution’s mean and spread, making it possible to compare values from different distributions or assess how unusual a particular value is.
Example
- With the default values shown above, this calculator returns: Z-Score ≈ 1.000.
Frequently Asked Questions
What does a z-score of 0 mean?
A z-score of 0 means the value is exactly equal to the mean of the distribution.
What is considered an unusual z-score?
In a normal distribution, values with a z-score beyond ±2 are relatively uncommon (roughly the outer 5%), and beyond ±3 are rare (roughly the outer 0.3%).