Weighted Average Calculator
Give each value a weight — percentages, credit hours, or counts — and get the weighted mean with the whole calculation written out: every product, both totals and the final division.
3 numbers recognised
The scores or measurements — separate with commas.
3 numbers recognised
One weight per value. They don't need to add up to 100.
Multiply each value by its weight, add the products (7,950), then divide by the total weight (100): the weighted average is 79.5.
Rounded where needed — the calculation itself is exact for the numbers you entered.
Pair each value with its weight
Your weights add up to 100, so they behave like percentages — each value contributes its share directly.
Value Weight Value × weight 90 20 90 × 20 = 1,800 85 30 85 × 30 = 2,550 72 50 72 × 50 = 3,600 Every value is multiplied by its own weight before anything is added.
Add the products, and add the weights
Two running totals: the weighted contributions on one side, the total weight on the other.
- Sum of value × weight
- 7,950
- Sum of weights
- 100
Divide the two totals
Dividing by the total weight is what rescales everything — it plays the role the count plays in a simple mean.
weighted average = 7,950 ÷ 100 = 79.5sum of products ÷ sum of weights
Compare with the unweighted mean
The simple mean treats every value equally; the weights pull the answer toward the heavily weighted values, moving it from 82.333333 to 79.5.
- Weighted average
- 79.5
- Simple (unweighted) mean
- 82.333333
Works instantly in your browser — nothing is uploaded, and the URL keeps your numbers so you can share the exact worked example.
Why weight an average at all
A plain mean assumes every value matters equally, and plenty of real data doesn't work that way. A final exam worth half the course should move your grade more than a quiz worth 5%; a fund that is 80% of a portfolio should drive the portfolio's return.
The weighted average fixes this with one idea: multiply before you add. Each value is scaled by how much it matters, and dividing by the total weight brings the answer back to the original units.
The grade-book example, worked
Say homework averages 90 and counts for 20%, the midterm was 85 at 30%, and the final was 72 at 50%. The products are 1,800, 2,550 and 3,600, which add to 7,950. The weights add to 100, so the course grade is 79.5.
Notice the pull: the simple mean of 90, 85 and 72 is about 82.3, but the heavily weighted final drags the true grade down three points. That gap between the simple and weighted mean is exactly what the last step of this calculator shows.