Z-Score Calculator
A z-score measures how many standard deviations a value lies from the mean. This calculator applies z = (x − μ) / σ and explains whether the value is above or below the mean and by how much.
Frequently asked questions
What does a z-score tell you?
It expresses a value's distance from the mean in standard-deviation units, allowing comparison across different data sets.
What is a negative z-score?
A negative z-score simply means the value is below the mean; a positive one means it is above.
What is considered an unusual z-score?
Values with |z| greater than about 2 are often treated as unusual, since they fall outside roughly 95% of a normal distribution.