Z-Score Calculator
Calculate how many standard deviations a value is from the mean (its z-score).
Calculate
Enter your values below.
Result
Z-score
0
Formula used
z = (value − mean) ÷ standard deviation
Example: value 85, mean 75, std dev 5 → z = 2.
How to use this calculator
- Enter Value, Mean, Standard deviation.
- Press Calculate to see your result instantly.
FAQ
Frequently asked questions
What does a z-score mean?
How many standard deviations a value is above (positive) or below (negative) the mean.
What does a z-score of 0 mean?
The value equals the mean exactly.
What's considered an unusual z-score?
Values beyond ±2 or ±3 are often considered statistically unusual, depending on context.
Why must standard deviation be positive?
A standard deviation of 0 would mean every value is identical, making z-score undefined.