Using the Z-score Calculator
A positive result is above the mean, a negative result is below it, and zero sits at the mean. The magnitude tells you how many standard deviations separate the value from that center.
Worked example
Use the example inputs below to reproduce this result. These are the form's starting values, not recommended targets. Changing your inputs updates your result above; this worked example stays fixed for comparison. Results are rounded for display.
Example inputs
- Value
- 85
- Mean
- 70
- Standard deviation
- 10
Example result
- Z-score
- 1.5
Method and assumptions
z = (value − mean) / standard deviation.
Check what the data represents
A statistical result is only meaningful in relation to the observations and assumptions behind it. Keep track of whether values describe a whole population or a sample, whether observations are independent, and which distribution the method uses. More decimal places cannot compensate for a sample that does not represent the question you are trying to answer.
Common question
Can the standard deviation be zero?
Not for this calculation. With no spread, dividing a difference by the standard deviation is undefined, so a positive standard deviation is required.
Guide updated .