Averaging percentages correctly often requires weighting each one by its sample size — a plain unweighted average can give a misleading answer.
How it works
Each percentage is multiplied by its weight, the products are summed, and the total is divided by the sum of the weights.
What this does not include
This does not include a plain unweighted average of any numbers — for that, use this site’s general average calculator (mean, median, mode) instead.
How to use this calculator
- Enter each percentage along with its weight (like number of questions or sample size).
A worked example
A 30-question test scored 85%, and a 5-question quiz scored 60%.
Weighted average = (85 × 30 + 60 × 5) ÷ (30 + 5) = (2,550 + 300) ÷ 35 = 81.43% — noticeably closer to the 30-question test’s score, since it carries far more weight.
What the variables mean
| Variable | Meaning |
|---|---|
| Percentage | The score for that group |
| Weight | How much that group counts — often a sample size or point value |
Edge cases worth knowing
A plain (unweighted) average of the same two scores would read 72.5% — misleadingly far from the 81.43% weighted figure, since a plain average lets the tiny 5-question quiz count just as much as the 30-question test.
Equal weights collapse this to a plain average — when every group carries the same weight, the weighted and unweighted results are identical.
Frequently asked questions
Why not just average the percentages directly?
A plain average treats a 30-question test the same as a 5-question quiz — weighting by sample size gives a more accurate combined result when the underlying groups are different sizes.
What happens if all weights are equal?
The weighted average reduces to the same result as a plain unweighted average, since every value counts equally either way.
What’s a practical use for this?
Combining several test or assignment scores worth different numbers of points into one overall percentage grade.
