Calculate the z-score of a value from the mean and standard deviation, and the share of a normal distribution below and above it. Enter your values; the result updates as you type, with the method shown below.
Formula
z = (x − μ) / σ
Worked example
x = 85, μ = 70, σ = 10: z = 1.5, about 93.3% below.
Frequently asked questions
What does z = 2 mean?
The value is 2 standard deviations above the mean.
Is a negative z-score bad?
It only means below the mean.
Does it need a normal distribution?
The percentages do.
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Results are estimates for information only. Check important figures with a professional.