Z-Score Calculator
Standardise a value against a distribution.
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Step by step
The formula
z = (x − μ) / σ
A z-score re-expresses any value as “how many standard deviations from the mean”, which lets you compare scores from completely different scales — a test mark against a height, say. Roughly 68% of a normal distribution falls between z = −1 and +1, and 95% between −2 and +2.
All calculations run locally in your browser and update instantly as you type.
Example calculations
Common questions this calculator answers — select one to load its values.
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Frequently asked questions
What does a z-score mean?+
It tells you how many standard deviations a value is above (positive) or below (negative) the mean.
All calculations run locally in your browser. Nothing you type is sent to a server.