How to calculate a weighted average
A weighted average gives some values more influence than others. Multiply each value by its weight, add up the products, then divide by the sum of the weights. For 80, 90, 70, 100 with weights 1, 2, 1, 1 the products are 80, 180, 70, 100 (sum 430) and the weights total 5, so the result is 430 ÷ 5 = 86. A plain mean would give 85. When every weight is the same, the answer is identical to the plain mean from the average calculator.
How to use this calculator
Enter each value with its weight and leave unused rows blank. Heavier weights pull the result toward those values. When every weight is equal the weighted average equals the simple mean — see the geometric mean calculator for a different kind of average.
Only the relative sizes of the weights matter, so weights of 1, 2, 1, 1 give the same answer as 10, 20, 10, 10.
Where weighted averages are used
Weighted averages appear in grade point averages, portfolio returns, and survey scoring, where each item counts differently. For a spread-aware central value, compare with the harmonic mean calculator.
In a course, weights are the percentage each assessment contributes to the final grade; in a portfolio, they are the share of capital in each holding.
Frequently asked questions
- How do I calculate a weighted average?
- Multiply each value by its weight, sum the products, then divide by the total weight. For 80, 90, 70, 100 with weights 1, 2, 1, 1 the result is 86.
- How is it different from a simple average?
- A simple average treats every value equally; a weighted average lets some values count more by assigning larger weights.
- Can weights be decimals or percentages?
- Yes. Any positive numbers work as weights — the calculator divides by their total, so percentages or fractions are fine.
- What if all weights are equal?
- Then the weighted average equals the simple arithmetic mean of the values.
- What happens if I give a value a weight of zero?
- It is excluded from the result entirely, because its product contributes nothing to the numerator and nothing to the total weight. That is a convenient way to drop a value without deleting it, but every weight cannot be zero — the total must be non-zero.