Z-Score Calculator
Find the z-score of a value from the mean and standard deviation, and the share of a normal distribution below and above it.
Z-score
1.5
- Share of values below
- 93.32%
- Share above
- 6.68%
- Within ±z of the mean
- 86.64%
85 is 1.5 standard deviations above the mean, higher than about 93.3% of a normal distribution.
How it's worked out
- Z-score
(85 − 70) ÷ 101.5 - Normal distribution
area under the bell curve to the left of z93.32%
- The percentages assume the values follow a normal (bell-shaped) distribution.
The formula
z = (x − mean) ÷ standard deviation
Worked example
A mark of 85 where the mean is 70 and the standard deviation 10 has z = 1.5, higher than about 93.32% of a normal distribution.
Questions people ask
What is a z-score?
How many standard deviations a value is from the mean. A z-score of 1.5 is one and a half standard deviations above average.
How do I calculate a z-score?
Subtract the mean and divide by the standard deviation: (85 − 70) ÷ 10 = 1.5.
What percentile is a z-score of 1.5?
About the 93rd: 93.3% of a normal distribution lies below it.
About this calculator
Formula and rules last checked 25 October 2026Written and tested by the CalculatorDex teamReport a problem