Z-Score Calculator
Fill in the values and the answer updates as you type.
How the Z-Score Calculator works
z = (value − mean) ÷ standard deviation. Percentiles assume a normal (bell curve) distribution and use a numerical approximation of the normal CDF, accurate to roughly 6 decimal places. Example: with the default values, z-score comes to 1.5.
Inputs and results
The Z-Score Calculator takes 3 inputs and gives 3 results.
What you enter
- Value — starts at 85.
- Mean — starts at 70.
- Standard deviation — starts at 10.
What you get
- Z-score
- Percentile (share below)
- Share above
Example: Z-Score Calculator with the starting values
With value 85, mean 70 and standard deviation 10, the calculator returns:
| Z-score | 1.5 |
|---|---|
| Percentile (share below) | 93.32% |
| Share above | 6.68% |
Change any value above and the results update straight away.
Z-Score Calculator FAQ
How do I use the Z-Score Calculator?
Enter value, mean and standard deviation in the fields, then read z-score, percentile (share below) and share above in the result panel. The answer updates as you type, and you can press Calculate or Enter to refresh it. Use “Copy link” to share your exact numbers with someone else.
What does the Z-Score Calculator calculate?
Find how many standard deviations a value is from the mean. It returns z-score, percentile (share below) and share above from the 3 values you provide.
What values does the Z-Score Calculator start with?
It opens with value 85, mean 70 and standard deviation 10 so you can see a working result straight away. Replace them with your own numbers, or press Reset to return to these starting values.
Is the Z-Score Calculator free and private?
Yes. It is free, needs no account, and runs in your browser, so nothing you type is sent to or stored on our servers. See the Privacy Policy for details.
Can I rely on the Z-Score Calculator for important decisions?
Treat the result as a well-rounded estimate. Real situations often have details a general calculator cannot know, so confirm important decisions with a qualified professional. See the Disclaimer for more.