How to calculate the average (mean)
Updated on June 18, 2026 · by Rafael Rossi
An average condenses a set of values into a single number representing its "center". It's one of the most-used calculations — from school grades to prices and sports stats.
Arithmetic mean (the common one)
mean = sum of values ÷ number of values
Example: grades 8, 6 and 10 → (8 + 6 + 10) ÷ 3 = 8.
Weighted mean
When values have different weights (one exam worth more), multiply each by its weight, add, and divide by the sum of weights:
mean = Σ(value × weight) ÷ Σ(weights)
Example: grades 8, 6, 9 with weights 2, 3, 5 → (16 + 18 + 45) ÷ 10 = 7.9.
Mean or median?
The median is the middle value of the sorted list. With outliers, it represents the "typical" value better than the mean — which is why incomes and house prices are usually reported by the median.
The outlier effect
Salaries of 7, 8, 9 and 50 (thousand): the mean jumps to 18.5, but the median stays at 8.5 — far more faithful to the group.
FAQ
Do weights have to add to 10 or 100? No. Any numbers work; the formula divides by their sum.
Mean vs geometric mean? The geometric mean multiplies values and takes a root — used for growth rates and returns, not grades.