Mean Calculator

Mean = (x1 + x2 + x3 + ... + xn) / n

The arithmetic mean is the most widely used measure of central tendency, commonly called “the average.” You add up all the values and divide by how many values there are.

What the variables mean:

• x1, x2, … xn – the individual numbers in your data set
• n – the total count of numbers

When to use the mean: The mean is useful whenever you want a single number that represents the “typical” value in a data set. Common uses include calculating grade averages, average temperatures, average prices, and sports statistics.

Practical examples:

• Test scores: If your scores are 85, 90, 78, 92, and 88, the mean is (85+90+78+92+88)/5 = 86.6
• Daily temperatures: Monday through Friday temperatures of 72, 75, 68, 70, 80 give a mean of 73 degrees.

Tips and common mistakes:

• The mean is sensitive to outliers. One very high or very low value can pull the average significantly. For example, incomes of $40K, $45K, $50K, $42K, and $500K produce a mean of $135.4K, which does not represent the typical person in the group.
• When outliers are present, the median (middle value) is often a better measure of center.
• Do not confuse the mean with the mode (most frequent value) or the median (middle value when sorted).
• Separate your numbers with commas, spaces or line breaks. A column copied out of a spreadsheet pastes in directly. The calculator shows the sum and the count so you can check the arithmetic yourself.
• The mean works with negative numbers too – they simply reduce the sum.

A trap worth knowing about: an empty slot is not the same as a zero. If a spreadsheet column has blank cells and you paste it somewhere that reads the blanks as zeros, every blank drags the average down. Six people scoring 80 and four blanks gives 48, not 80. This calculator ignores empty pieces entirely, so stray commas and blank lines cost you nothing, but plenty of tools do not. Check the count the calculator reports against the number of values you meant to enter. If they disagree, the mean is answering a different question from the one you asked.