Average Calculator

Mean, median and mode explained

An average describes the typical value in a set of numbers, but there are three common ways to calculate it and they can give different answers.

• Mean is the sum of all values divided by how many there are.
• Median is the middle value when the numbers are sorted. With an even count, it is the mean of the two middle values.
• Mode is the value that appears most often.

Worked example

For 10, 20, 30, 40, 50 the mean is 150 ÷ 5 = 30 and the median is also 30. Now replace the last value with 500: the numbers are 10, 20, 30, 40, 500. The mean jumps to 120, but the median stays at 30. This is why the median is a better summary when a few values are extreme, such as incomes or house prices.

Which one should you use?

• Use the mean for evenly spread data such as test scores in one class.
• Use the median when outliers exist.
• Use the mode for categories, such as the most common shoe size.

Frequently asked questions

How do I calculate a weighted average?

Multiply each value by its weight, add the results and divide by the sum of the weights. Marks in a course with different exam weightings are a typical case.