Statistics

Z-Score Calculator

Calculate z-score, probability (p-value), and percentile for any data point in a normal distribution.

Inputs

Data Point (x)

Mean (μ)

Standard Deviation (σ)

Results

—

Z-Score

P(X < x) — Cumulative—

P(X > x) — Upper Tail—

Percentile—

Interpretation—

What is a Z-Score?

Z = (x − μ) / σ. A z-score tells how many standard deviations a value is from the mean. Z=0 is exactly average. Z=1 means 84th percentile. Z=2 means 97.7th percentile. Z=−1 means 16th percentile. Used in hypothesis testing, quality control, and standardized exams.