Average Calculator

What does this Average Calculator do?

This tool calculates three of the most common measures of "central tendency" for any list of numbers you enter: the mean (what most people mean by "average"), the median (the middle value), and the mode (the most frequently occurring value).

The formulas

• Mean = (sum of all values) ÷ (count of values)
• Median = the middle value once the data is sorted (or the average of the two middle values if there's an even count)
• Mode = the value(s) that appear most often in the data set

Step-by-step example

For the data set 12, 18, 9, 24, 15: sum = 78, count = 5, so mean = 78 ÷ 5 = 15.6. Sorted, the data is 9, 12, 15, 18, 24 — the middle value is 15, so median = 15. Since every value appears exactly once, there's no single mode (or every value is a mode, depending on convention).

Tips & common mistakes

• The mean is heavily skewed by outliers — a single very large or very small number can pull it far from what "typical" looks like. The median is more resistant to outliers.
• Always sort your data before finding the median by hand — it's a common mistake to eyeball the "middle" of an unsorted list.
• A data set can have more than one mode (bimodal, multimodal) or no meaningful mode at all if every value is unique.

Frequently asked questions