Z-Score Calculator
When you need to check z Score, the Z Score gives you a clear starting point. Enter one realistic example first, then compare another option if useful.
Z-score
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Percentile —
Interpretation —
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How it works
z = (x − μ) ÷ σ; percentile = Φ(z)How to use the Z Score
Enter the requested values and start with one realistic example. Read the result together with its unit or label, then change one input at a time if you want to compare options.
Review the assumptions on the page and confirm any result that affects money, safety, technical work or another important decision.
Frequently Asked Questions
What does a z-score tell you?
How unusual a value is: z = 0 is exactly average, z = +1 beats about 84% of a normal population, z = +2 beats about 97.7%. Negative scores mirror below the mean.
How do I convert a z-score to a percentile?
Look up (or compute) the standard normal cumulative probability Φ(z). This calculator does it with a high-accuracy approximation of the error function.
Where are z-scores used?
Standardized testing, quality control, medical growth charts, finance risk models — anywhere values from different scales must be compared on one footing.