Z Score Calculator
Calculate z score quickly with clear inputs, an instant result, and a practical formula.
Z Score measurements
Enter your values, then calculate.
Result
How to calculate z score
This calculator finds a Z-score, showing how many standard deviations an observed value is from the population mean.
How the calculation works
Z-score = (Observed value − Mean) ÷ Standard deviation.
Example
An observed value of 78, with a population mean of 65 and standard deviation of 8: (78−65)÷8 = 1.625.
Frequently asked questions
How is Z-score calculated?
Z-score = [Deviation from mean] ÷ [Standard deviation].
Is the Z Score Calculator free to use?
Yes — every calculator on Simple Calculator Tools is free, runs in your browser, and does not require an account.
Z Score Calculator
Z-score = (Observed value − Mean) ÷ Standard deviation.
Let's understand your z score result.
Calculate a result above and this guide will help you interpret it using this calculator's own formula and explanation.
Pro Tips for Z Score
- A Z-score of 0 means the value equals the mean exactly; positive Z-scores are above the mean, negative are below.
- Z-scores allow comparison of values from different distributions with different means and standard deviations, by putting them on a common standardized scale.
Common Z Score Mistakes to Avoid
- Comparing raw values from two different distributions directly instead of converting both to Z-scores first, which isn't a meaningful comparison unless the distributions share the same mean and standard deviation.
When to Use This Calculator
This calculator finds a Z-score, showing how many standard deviations an observed value is from the population mean.