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Z-Score Calculator
Turn a value into a standard score from the mean and standard deviation, with the percentile and probability below it.
Standard score
Z-score: —
Percentile: — · Probability below: —
Distance from the mean: —
How to use the Z-Score Calculator
- Enter the value you want to convert into a z-score.
- Set the mean and the standard deviation of the distribution.
- Read the z-score, percentile and probability in the result panel.
Features
- Standard score from value, mean and deviation
- Percentile and probability below the value
- Shows the distance from the mean
- Runs locally, no uploads
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Frequently Asked Questions
Common questions about the free online z-score calculator.
Enter your value, the mean and the standard deviation, and the standard score appears
instantly.
The value sits one standard deviation above the mean, which covers about 84 percent of a
normal distribution.
There is no good or bad score. A positive z-score is above the mean and a negative one is
below it.
The percentile is the share of a normal distribution that falls below your value, so a
z-score of 0 gives 50.
The z-score is undefined, because every value in the distribution is identical and there is
no spread.
A z-score uses the true population standard deviation, while a t-score is used with small
samples.
Yes. A negative z-score simply means the value is below the mean of the distribution.
They standardise scores from different scales so that results can be compared directly with
one another.
No. Every figure is worked out locally in your browser and nothing is transmitted.
Yes. It is completely free and unlimited, with no account, no sign-up and no usage caps.
Last updated: October 10, 2026