Statistics
Z-score Calculator
Use this z-score calculator to standardize a value and estimate where it falls on a normal distribution.
Try an example
Result
Z-score
—
- Approx. percentile
- —
- Distance from mean
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Study path
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What the z-score calculator solves
Use this How many standard deviations a value sits above or below the mean. calculator to standardize a value and estimate where it falls on a normal distribution.
Formula
How to use it
- Enter the value.
- Enter the mean.
- Enter A number saying how far, on average, the data values sit from the mean..
How to read the answer
A positive z-score is above the mean. A negative z-score is below the mean. The size tells how many standard deviations away the value sits.
Common mistakes and edge cases
- Standard deviation must be greater than zero.
- The percent of values in a data set that fall at or below a given value. assumes a normal distribution.
- Z-score measures standard deviations, not raw units.
Worked examples
Above average score
Z-score
1
Below average score
Z-score
-1.5
Frequently asked questions
What does z = 2 mean?+
The value is two standard deviations above the mean.
Is percentile exact?+
It is exact only if the data follows the normal distribution model. For skewed or unusual data, treat the percentile as a model-based estimate.
About this calculator
- Written by
- mathcheck editorial team
- Last reviewed
- May 8, 2026
Method
- Uses the values entered by the user and stable formulas documented on the page.
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Last updated: May 8, 2026