Z-Score Calculator
Compute z-scores from raw data, convert between z-scores and probabilities (z-table), and find probability between two z-scores.
Z-score Calculator
Compute the z-score of a normal distribution.
Z-score and Probability Converter
Enter any one value to convert between z-score and probabilities (z-table equivalent).
Probability between Two Z-scores
Find the area P between two z-scores on the standard normal curve.
Formula
z = (x − μ) / σ
What is a z-score?
A z-score (standard score) tells you how many standard deviations a value is from the mean. A z-score of 0 is the mean; z = 1 is one standard deviation above the mean.
z = (x − μ) / σ
Z-table and probabilities
The standard normal distribution has mean 0 and standard deviation 1. P(x < Z) is the cumulative area to the left of Z — what a z-table provides. This calculator converts between z-scores and common probability regions.
Interpreting z-scores
- |z| < 1: within one standard deviation (common)
- |z| < 2: about 95% of normal data
- |z| > 3: unusual / outlier territory
Frequently Asked Questions
The area between −Z and +Z under the standard normal curve. For Z=1.96, this is about 95%.
Yes. Use the Z-score and Probability Converter — enter exactly one field and click Calculate.