How is it calculated?
z = (x − μ) ÷ σ
A z-score of 0 is exactly average; +1 is one standard deviation above. About 68% of values lie within ±1, 95% within ±2 and 99.7% within ±3.
Z-score calculator
Enter a value, the mean and the standard deviation. The calculator gives the z-score and where the value sits on the normal curve.
Last updated: · By Furkan Çetinkaya · About & Methodology
Z-score
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Common questions
What is a good z-score?
It depends on context. In test scores, z = 1 is about the 84th percentile; z = 2 about the 98th.
Can a z-score be negative?
Yes — negative means below the mean.