Convert a raw value into a z-score and percentile, so you can see how far above or below average it sits and what proportion of the distribution it beats.
How to use it
Enter the value you are interested in, along with the mean and standard deviation of the distribution it comes from. The calculator returns the z-score and the corresponding percentile.
How to read the result
A z-score is the number of standard deviations a value sits from the mean. A positive z is above average, negative is below. The percentile tells you what share of the distribution the value exceeds — the 84th percentile beats about 84% of cases.
Rather have it done for you?
Send us your data and a qualified statistician will run the analysis and write it up. Fixed price, by email.
Frequently asked questions
What is a z-score?
It standardises a value by expressing it in standard-deviation units from the mean. This lets you compare values from different distributions on a common scale.
What counts as a high or low z-score?
Roughly, z-scores beyond ±2 are unusual (outside about 95% of the distribution) and beyond ±3 are rare. Context matters, but those are useful rules of thumb.
Can I go from a percentile back to a value?
Yes, that is the inverse calculation. If you need it for a specific dataset, send us the details and we will work through it with you.