Z-Score Calculator

Added 2026-08-29

Calculate a z-score from a value, mean and standard deviation and view cumulative and upper-tail normal probabilities.

✓ Runs locally in your browser✓ No account or dataset upload required✓ Effect sizes / uncertainty shown where appropriate

Observed value (x)

Mean (μ)

Standard deviation (σ)

Z-score

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P(X ≤ x)

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P(X ≥ x)

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Statistical output is a calculation aid. Check assumptions, study design and reporting requirements before drawing scientific conclusions.

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Use Ctrl + Y / Ctrl + Shift + Z to redo an action after Undo. A small habit that keeps keyboard-heavy work moving.

About this tool

Calculate a z-score from a value, mean and standard deviation and view cumulative and upper-tail normal probabilities.

Common uses

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How it works

1Enter or paste the requested sample values, summary inputs or contingency data.
2Choose the method, confidence level or test options when available, then run the calculation.
3Review the estimate/test statistic together with p-value, confidence interval, effect size and method notes where available.

Does this statistics calculation upload my data?

No. Entered values are processed locally in your browser with JavaScript.

Should I interpret statistical significance by itself?

No. Review effect size, confidence intervals, study design, assumptions, sampling and multiplicity together with the p-value.