Average Calculator

Paste a list of numbers to get the mean, median, mode, range, sum and standard deviation instantly.

  • Reviewed October 2026
  • Formula and worked example below
  • Free, no sign-up, runs in your browser
Enter your numbers to see the result.

Three kinds of average

  • Mean is what most people call "the average": add all the values and divide by how many there are.
  • Median is the middle value once the list is sorted. With an even count, it is the mean of the two middle values.
  • Mode is the value that appears most often. A list can have more than one mode, or none.

For 12, 15, 18, 18, 21, 24, 30: the sum is 138, so the mean is 138 ÷ 7 = 19.71. The median is the 4th value, 18. The mode is also 18, and the range is 30 − 12 = 18.

Mean or median?

The mean is pulled toward extreme values; the median is not. That is why house prices and incomes are usually reported as medians: a few very high values would make the mean misleading. If the mean and median are far apart, your data is skewed.

Standard deviation

Standard deviation measures how spread out the numbers are around the mean. A small value means the numbers are clustered together; a large value means they are spread out.

σ = √( Σ(x − mean)² ÷ N ) s = √( Σ(x − mean)² ÷ (N − 1) )

Use the population version (σ, divide by N) when your list contains every value you care about. Use the sample version (s, divide by N − 1) when your list is a sample drawn from a larger group, as in most surveys and experiments.

Geometric mean

For growth rates and ratios, the geometric mean is more appropriate than the arithmetic mean. It multiplies the values and takes the Nth root, and is shown when all your numbers are positive.

Frequently asked questions

How do I calculate the average of numbers?

Add all the numbers together and divide the total by how many numbers there are. That gives the arithmetic mean.

When should I use the median instead of the mean?

Use the median when your data has outliers or is skewed, such as incomes or house prices, because it is not affected by extreme values.

What is the difference between sample and population standard deviation?

Population standard deviation divides by N and describes a complete data set. Sample standard deviation divides by N − 1 to correct for bias when estimating from a sample.

Add this calculator to your website

Free to use on blogs, school sites and company intranets. Copy this code into your page:

Last reviewed Oct 20, 2026. Results are estimates; check important decisions with a qualified professional.