Access Free Tools

Home / Blog / Z-score calculator guide

Z-score calculator guide

How to use the Z-score Calculator

The Z-score Calculator standardizes a value by comparing it with the mean and standard deviation, then estimates its normal percentile.

Open the z-score calculator

Quick start

  1. Enter the value you want to standardize.
  2. Enter the mean.
  3. Enter the standard deviation.
  4. Press Calculate z-score and review the direction and percentile.

Reading a z-score

A positive z-score means the value is above the mean. A negative z-score means the value is below the mean.

The size of the z-score tells how many standard deviations the value is from the mean.

Percentile estimate

The percentile is an approximate area to the left of the z-score on a standard normal curve.

Use it as a quick estimate for normal-distribution examples, not as a substitute for a full statistics report.

Examples from the calculator

Above average x=85, mean=70, SD=10

z = 1.5

At the mean x=70, mean=70, SD=10

z = 0

Below average x=55, mean=70, SD=10

z = -1.5

History, privacy, and copying

Recent answers stay visible in the page while you work. The history is kept only in the current browser tab and is not sent to a server.

Copy answer copies the expression and result so you can paste it into notes, homework, a message, or another document.