Standard Deviation Calculator
Calculate variance and standard deviation for sample or population data.
How to use Standard Deviation Calculator
Three quick steps — no sign-up needed
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Step 1
Enter your data set
Paste numbers separated by commas, spaces, or new lines.
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Step 2
Choose sample or population
Sample uses n-1 (sample SD); population uses n - pick the definition your course requires.
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Step 3
Read variance and SD
See variance and standard deviation for the selected definition.
About Standard Deviation Calculator
Standard Deviation Calculator computes variance and standard deviation for a numeric list, with a toggle between sample and population definitions. Statistics students searching "standard deviation calculator", "sample vs population SD", or "variance calculator" need the correct denominator choice.
Enter numbers, then select Sample (divides by n-1) or Population (divides by n). Sample SD estimates spread from a subset; population SD describes an entire set. Using the wrong one is a common exam mistake.
SD is in the same units as the data; variance is squared units. Outliers inflate both - consider median absolute deviation when distributions are skewed, in more advanced work.
Descriptive statistics helper - not a full stats package for hypothesis tests.
Benefits of Standard Deviation Calculator
Frequently asked questions
When do I use sample standard deviation?
When your data is a sample and you estimate the wider population - typically divide by n-1.
When is population SD correct?
When the data is the entire population of interest - divide by n.
What is variance?
The average squared deviation from the mean (with sample or population denominator as chosen).
Can I enter decimals?
Yes - use a clean list of numeric values.
Does this run t-tests?
No - only variance and standard deviation for the list.