Z-Score Calculator
Find a z-score from a raw value, or convert a z-score back into a raw value.
Reviewed by the WorldCalcs team · Methodology · Last reviewed: June 2026
Result
z = (x − μ) / σ
z = 1.5
What is a z-score?
A z-score (or standard score) tells you how many standard deviations a value sits above or below the mean. A positive z-score is above average, a negative one is below, and zero is exactly average. It lets you compare values from different data sets on the same scale.
How it's calculated
Subtract the mean from your value, then divide by the standard deviation: z = (x − mean) / standard deviation. To go the other way and find the raw value for a given z-score, rearrange to x = mean + z × standard deviation. The standard deviation must be greater than zero.
Example
A test score of 85 in a class with mean 70 and standard deviation 10: z = (85 − 70) / 10 = 1.5, so the score is 1.5 standard deviations above average. Going back: a z-score of 2 with the same mean and standard deviation gives x = 70 + 2 × 10 = 90.
All calculations happen in your browser. Nothing is sent, stored, or tracked.
Results are estimates and may contain errors — for general information only, not professional advice. Always verify before relying on them. Disclaimer
How to use
Choose Find z and enter your value, the mean and the standard deviation, or choose Find x and enter a z-score, mean and standard deviation to recover the raw value.
The standard deviation must be greater than zero.