How to use Weighted Average Calculator
Weights control each value’s influence on the result. They may be credits, frequencies or relative percentages. The total weight does not have to be 100 because the calculator divides by the sum of all weights.
The lists must have the same length and every weight must be positive. Keep values on the same scale. A negative value is supported, but a negative weight is not part of this ordinary weighted-average model.
The formula
Weighted average = sum(value × weight) / sum(weights)
A worked example
Values: 70, 80, 90 · Matching weights: 20, 30, 50
Weighted average: 83
Questions about this calculation
Must weights total 100?
No. Weights of 2, 3 and 5 produce the same average as 20, 30 and 50.
What if a value has no weight?
Omit it. This tool requires one positive weight for every listed value.
Formula checks: 2026-10-08. Assumptions & corrections.