Standard Deviation Calculator
Standard deviation calculator: enter up to five values to get sample or population standard deviation, variance and the mean.
Editorial review: Farrow (pseudonym; identity and professional credentials are not disclosed). This page is for educational purposes, not professional advice.
Your inputs
Results update as you type. Nothing you enter leaves your device.
Results
- Variance
- 1.2
- Mean
- 3.8
Example with the starting values
These results use the calculator's initial inputs. Change the values above to calculate your own estimate.
Inputs
- Data is a
- Sample
- Value 1
- 2
- Value 2
- 4
- Value 3
- 4
- Value 4
- 4
- Value 5
- 5
Results
- Standard deviation
- 1.0954
- Variance
- 1.2
- Mean
- 3.8
How does the Standard Deviation Calculator work?
Standard deviation measures how far values spread from their mean. Find the mean, square each value's distance from it, average those squares (the variance), then take the square root.
Population uses N in the denominator and sample uses N − 1. For 2, 4, 4, 4, 5 the mean is 3.8, the sum of squares is 4.8, the sample SD is 1.0954 and the population SD is 0.9798.
Frequently asked questions
Sample or population standard deviation?
Use population when your data is the whole group, and sample when it is a subset drawn from a larger one. Sample divides by N − 1.
What is variance?
Variance is the standard deviation squared, the average squared distance from the mean. Its units are the data's units squared.
What is a low standard deviation?
A low value means the numbers cluster close to the mean. A high value means they are spread out.
What is the 68-95-99.7 rule?
In a normal distribution about 68% of values fall within one standard deviation of the mean, 95% within two and 99.7% within three.