Z-Score Calculator
Enter a data value, population mean, and standard deviation to calculate the z-score and p-value.
Z-Score — Formula & Guide
Formula
z = (x − μ) / σ
Where x = data point, μ = mean, σ = standard deviation.
Interpretation
z = 0: value equals the mean • z = +1: one SD above the mean • z = −1: one SD below the mean.
For a standard normal: 68% of data falls within z = ±1, 95% within z = ±1.96.
