Average Calculator Guide

Learn how to calculate a mean and median, when each measure is useful, and how outliers can change an average.

An average is a compact way to summarize a group of numbers, but there is more than one way to describe what is typical. The arithmetic mean adds all values and divides by the number of observations. The median sorts the values and selects the middle position, or the midpoint of the two middle values when there is an even number of observations.

When the mean is useful

The mean is useful when every observation should contribute proportionally to the summary. For example, if five delivery times are 20, 22, 24, 26 and 28 minutes, the mean is 24 minutes. Because the mean uses every value, it can be useful for comparing repeated measurements.

When the median can be better

The median is less affected by an unusually high or low value. Imagine four ordinary expenses and one very large expense. The mean may move upward substantially, while the median can remain closer to the amount that represents a typical observation.

Common mistakes

Do not forget to include or exclude values consistently. A blank entry should not silently be treated as zero, and numbers should use the same units. When comparing two averages, make sure the underlying groups and time periods are comparable.

Check the result before using it

A calculator is most useful when the inputs match the question you are trying to answer. Check units, dates, rates, periods and rounding before copying a result into a document or decision. For financial calculations, compare the estimate with the actual terms supplied by a lender, employer, bank or other provider. For documents and images, keep the original file and inspect the processed copy before sharing it.

Use the related UniConvertHub tool

The interactive Average Calculator Guide tool is designed to make the calculation or file task quick to test in a browser. You can also browse the full guide library for related explanations.