Enter a value, mean, and standard deviation to calculate the z-score.
How to Use the Z-score Calculator
Value, mean, and standard deviation are the three fields — the same three numbers a z-table lookup needs, just computed instead of looked up.
z = (x − mean) ÷ standard deviationAn 85 in a data set averaging 75, with a standard deviation of 10, gets a z-score of exactly 1.0 — one full standard deviation above typical. That's the entire appeal of a z-score: it takes a raw number and says how unusual it actually is, not just what it is.
Positive means above the mean, negative means below, and 0 means dead center. What makes z-scores genuinely useful is that they strip away units — a z-score of 2 means "two standard deviations above average" whether the underlying data was dollars, test points, or centimeters, which is exactly what lets you compare how unusual two completely different measurements are on the same footing. This Z-Score Calculator handles the conversion.