Convert a raw score into a standard score using the mean and standard deviation.
| z | – |
Use this calculator to standardise a measurement so you can compare it with a reference mean and spread. A z-score says how many standard deviations a value sits above or below the mean. IQ scores, exam marks, and process measurements are common examples.
The formula is: z = (x − μ) / σ. Enter x, μ, and σ in the same units. An IQ of 115 with mean 100 and σ = 15 gives z = 1, one standard deviation above the mean. Negative z means below the mean.
This is a location on the standard scale, not a p-value. σ must be positive. The calculator does not assume a normal shape; normality matters only if you later read z against a normal table.
Value (x): Raw score to standardise.
Mean (μ): Reference mean of the group or process.
Standard deviation (σ): Reference spread; must be positive.
z: Standard score, (x − μ) / σ.
Related calculators