Z-Score Calculator
Find how many standard deviations a value is from the mean.
Standardize any value
A z-score expresses how far a value sits from the mean in units of standard deviation, which lets you compare numbers measured on completely different scales. It is a cornerstone of statistics.
A test score of 85 with a mean of 70 and a standard deviation of 10 has a z-score of 1.5 — one and a half standard deviations above average. Positive scores are above the mean, negative below.
Exact and private
It applies the standardizing formula in your browser, so nothing you enter is uploaded.
Frequently Asked Questions
What is a z-score?
The number of standard deviations a value lies above or below the mean. A z-score of 2 means the value is two standard deviations above average.
What is the formula?
Z equals the value minus the mean, divided by the standard deviation.
What is it used for?
Comparing values from different scales, spotting outliers, and finding probabilities under a normal distribution.
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