Math & Scientific
Z Score Calculator
Z Score — it standardises a value with z = (x − μ) / σ, expressing how many standard deviations it sits from the mean. This page runs that same calculation on your numbers, in your browser: no signup, no uploads, nothing stored.
Z Score Calculator helps you work out a z-score. Enter your raw value, population mean and standard deviation and it returns the z-score instantly, right in your browser with nothing uploaded.
About this calculator
It standardises a value with z = (x − μ) / σ, expressing how many standard deviations it sits from the mean. That is the whole of the calculation — the mistakes happen in the inputs. It matters when you need the exact relationship checked quickly rather than worked through by hand. Worked example: A value of 85 with mean 70 and SD 10 has z = (85 − 70) ÷ 10 = 1.5 . Use the calculator with your own figures; it runs entirely on your device.
How to use
- Enter the value x.
- Enter the mean and standard deviation.
- Press Calculate to find the z-score.
- Read the z-score, the number of standard deviations x is from the mean.
Why use Z Score Calculator
Fast
Calculations run in your browser. No round trip to a server.
Private
Your inputs never leave your device. Nothing is uploaded.
Free
No signup, no paywall, no ads-in-results, no watermarks.
Accurate
Uses standard, well-established formulas; check critical results independently.
Mobile-ready
Optimised for phones, tablets, and desktops alike.
Transparent
Honest disclaimers wherever browser limits or regional rules apply.
Common uses
Use it when revising for exams
Use it when preparing worksheets
Use it for science-fair and project numbers
Z Score in competitive-exam practice
Use it for verifying answers from a textbook
Use it for understanding a formula's behaviour
Technical notes
Z Score Calculator standardises a value with z = (x − μ) / σ, expressing how many standard deviations it sits from the mean.
Inputs are taken exactly as entered, so check for typos before trusting an answer.
Nothing you type is uploaded — the calculation happens entirely on your device.
FAQ
What does a z-score tell me?
It tells you how many standard deviations a value lies above (positive) or below (negative) the mean.
Why must the standard deviation be positive?
The standard deviation measures spread and cannot be zero or negative, so the calculator requires a value greater than zero.
What counts as an unusual z-score?
As a rough guide, z-scores beyond about 2 in either direction are uncommon, and beyond 3 are rare for a normal distribution.
Does the Z Score Calculator send my data to a server?
No. The Z Score Calculator runs entirely in your browser, so nothing you enter is uploaded, stored, or shared.
Worked example
A value of 85 with mean 70 and SD 10 has z = (85 − 70) ÷ 10 = 1.5.