Average Calculator

The average (arithmetic mean) tells you the center of a data set — it is the value you would get if you spread the total equally across every item. Enter any list of numbers into this average calculator and it returns the mean instantly, with no manual arithmetic required.

How to use this calculator

1. Type your numbers into the input box, separated by commas, spaces, or line breaks (for example, 12, 15, 18, 20, 25).
2. The calculator adds all the values and divides by the count, then displays the Average result.
3. To start over, clear the box and enter a new set of numbers.

Worked example

Suppose five students scored the following marks on a test: 12, 15, 18, 20, 25.

Step 1 — add all the values:

sum = 12 + 15 + 18 + 20 + 25 = 90

Step 2 — divide by the number of values:

average = sum / n = 90 / 5 = 18

The average score is 18. If every student had scored the same, each score would be exactly 18 — that is what “center of the data” means in practice. For the formal definition and related measures, see the NIST/SEMATECH e-Handbook section on measures of location and the mean.

Frequently asked questions

What is the difference between average and mean?

In everyday use, “average” almost always refers to the arithmetic mean: add the numbers and divide by the count. Mathematicians distinguish between the arithmetic mean, geometric mean, and harmonic mean, but unless a problem says otherwise, “average” means the arithmetic mean.

How do I calculate average?

Add all the values together, then divide by how many there are. For the set 4, 8, 12, the sum is 24 and the count is 3, so the mean of numbers is 24 / 3 = 8.

Does the average work for negative numbers?

Yes. The formula sum / n applies to any finite numbers, including negatives. For example, the average of -3, 0, 9 is (-3 + 0 + 9) / 3 = 6 / 3 = 2.

When is the average misleading?

The mean is pulled toward extreme values (outliers). If one number is far above or below the rest — for example, four salaries of 30000, 32000, 31000, 500000 — the mean (148250) does not represent most of the values. In those cases, the median is often a better measure of center.