Mean, Median & Standard Deviation Calculator
Enter numbers separated by commas, spaces, or new lines to get the sum, mean, median, mode, min, max, variance, and standard deviation, for both a population and a sample. Add one score to see its T-score (deviation score, mean 50 and SD 10) based on your data as the population. Everything is calculated in your browser, and nothing you type is sent to a server. For ratios, try the Ratio Calculator; for unit math, try the Unit Converter.
🔒 Runs in your browser · Your data is never sent to a server
Full-width digits also work. Do not use thousands separators (1,000). Anything that is not a number is ignored.
Your data is treated as the whole population.
Notes
- The T-score is 50 + 10 × (score − mean) ÷ population standard deviation. Your data is treated as the entire population, so it will not match a real exam’s score, which uses all test takers.
- Commas are treated as separators, so type 1000 rather than 1,000.
- Decimal arithmetic can show tiny floating-point errors. Displayed values are rounded to 6 decimal places.
Glossary
Standard deviation
A measure of how far values spread from the mean. A larger value means more variation. It is the square root of the variance.
Population vs. sample variance
Population variance divides the squared deviations by n; sample variance divides by n − 1 to estimate the population from a sample. Use population when you have every value and sample when you have only a subset.
T-score
A score rescaled to a mean of 50 and a standard deviation of 10. The average scores 50, and one standard deviation above it scores 60.
Median and mode
The median is the middle value when sorted (the average of the two middle values when the count is even); the mode is the most frequent value. Both are less affected by outliers than the mean.
FAQ
How is the T-score (deviation score) calculated?
It is 50 + 10 × (score − mean) ÷ standard deviation, using the population standard deviation of the data you entered. A score equal to the mean gets 50, and one standard deviation above the mean gets 60.
Should I use the population or the sample standard deviation?
Use the population value when you have every data point, such as all scores in a class. Use the sample value when your data is a subset used to estimate a larger group; it divides by n − 1 instead of n. Both are shown.
Why does the mode say "None"?
When every value appears exactly once, there is no single most frequent value. If several values tie for the highest count, all of them are listed in ascending order.
What input format and size limits apply?
Numbers separated by commas, spaces, tabs, or new lines, up to 10,000 values. Negative numbers, decimals, exponent notation, and full-width digits work, but a comma is always a separator, so 1,000 is read as 1 and 000.
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