⚖️ Weighted Average Calculator
Add each value with its weight, as a percentage, points or quantity, and get the weighted mean plus the unweighted average for comparison.
Quick answer: Weighted average = Σ(value × weight) ÷ Σ(weights). With values 85, 90 and 78 at weights 30, 20 and 50, (2,550 + 1,800 + 3,900) ÷ 100 = 82.5.
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Weighted Average Calculator inputs
Result
Weighted average
82.5
3 values, total weight 100
| Sum of value × weight | 8,250 |
| Sum of weights | 100 |
| Weighted average | 82.5 |
- Simple average (unweighted)
- 84.33
- Difference
- -1.83
How a weighted average works
Multiply each value by its weight, add the results, then divide by the sum of the weights.
Weighted average = (v₁w₁ + v₂w₂ + …) ÷ (w₁ + w₂ + …)
Example: a course has homework 85 (30%), a midterm 90 (20%) and a final 78 (50%). The calculation is (85×30 + 90×20 + 78×50) ÷ 100 = (2,550 + 1,800 + 3,900) ÷ 100 = 82.5. The simple average, 84.3, overstates the result because the lowest score has the largest weight.
Common uses
| Use | Value | Weight |
|---|---|---|
| Course grade | Score | Percent of grade |
| Inventory cost | Unit price | Units bought |
| Portfolio return | Return of each asset | Amount invested |
| Survey score | Rating | Number of responses |
Tips
- Leave unused rows blank; a row needs both a value and a weight.
- Weights can be percentages, points or counts – only their proportions matter.
- Need a grade needed on the final? Use the grade calculator.
Frequently asked questions
Do the weights have to add up to 100?
No. The formula divides by the total weight, so weights of 3, 2 and 5 give the same answer as 30, 20 and 50.
How is a weighted average different from a normal average?
A normal average treats every value equally. A weighted average lets some values count more, such as a final exam worth 50% of a course.
How do I find the weighted average cost of inventory?
Enter each purchase price as the value and the units bought as the weight. The result is the average cost per unit.
Can a weight be zero?
Yes, a zero weight simply ignores that value, but the weights must add up to more than zero overall.
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