Z-Score Calculator
Calculate a z-score from a value, a mean and a standard deviation.
What is Z-Score?
A z-score says how many standard deviations a value sits from the mean: z = (x − mean) ÷ σ. It is what makes scores from different tests comparable — 85 on a test with mean 70 and σ 10 is z = 1.5, the same standing as 615 on a test with mean 600 and σ 10 — and it is the first step of every normal-distribution calculation.
How it works
Both ways of asking are supported. Supplied directly, the formula is applied as written. Supplied as a dataset, the mean and standard deviation are measured from the list first, so the two statistics the z-score is built on are reported rather than assumed — and the value being scored does not have to be one of the listed entries.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Realistic sample
Type or paste any realistic input — the tool computes the result locally and instantly.
Common mistakes
Expecting a server round-trip
Nothing is uploaded — every tool in this category runs entirely in your browser.