Z-Score Calculator
Convert a raw value to a z-score and find its percentile.
Results update as you type.
About this calculator
A z-score (standard score) tells you how many standard deviations a value lies above or below the mean: z = (x − μ) / σ. A positive z-score is above the mean, a negative one below. This calculator also returns the percentile — the probability that a value from a normal distribution is below x — using the standard-normal cumulative distribution.
Frequently asked questions
What does a z-score of 2 mean?
A z-score of 2 means the value is two standard deviations above the mean. Under a normal distribution about 97.7% of values fall below it, so it is a fairly extreme, high value.
Can a z-score be negative?
Yes. A negative z-score simply means the value is below the mean. A z-score of −1.5, for example, is one and a half standard deviations below the average.
Results are estimates for general guidance only, not financial, medical or tax advice.