Everyday utility

Z-Score Calculator

Calculate the z-score (standard score) and approximate percentile for a value relative to a normal distribution. Use this Data and utilities tool to enter your numbers, review the result, and understand the key assumptions before making the next decision.

What you get
A focused calculator, clear explanation, common questions, and useful next tools.
Quick intro
Calculator
Result
Explanation
Common questions
Related tools

Calculator tool

How this calculator works
The result depends on the numbers you enter and the assumptions shown below.

Z-score = (x − μ) / σ. It measures how many standard deviations a value is from the mean. A z-score of 0 = the mean; ±1 = 68.3% of data; ±2 = 95.5%; ±3 = 99.7%.

Review the inputs carefully and treat the output as an estimate. For decisions involving money, taxes, health, law, or security, compare the result with trusted professional guidance when needed.

Frequently asked questions

What is a good z-score?

It depends on context. In quality control, z-scores within ±3 are normal. In hypothesis testing, |z| > 1.96 means statistical significance at the 5% level (two-tailed).