Z-score Calculator
Standard score Z from value, mean and standard deviation.
How it works
Z = (x − μ) ÷ σ
Z is how many standard deviations a value is from the mean. Z = 1.5 means 1.5 SD above the mean.
Worked example
Score 85, mean 70, SD 10: z = (85−70) ÷ 10 = 1.5.
Under normality, z = 1.5 is about the 93.3rd percentile — above roughly 93% of people.
Notes and limitations
A z-score counts standard deviations from the mean, assuming approximate normality. With strong skew the percentile conversion misleads — read the empirical distribution instead.