Weighted Average Calculator
Enter up to 100 values and their weights to get the weighted average and each row’s share and contribution. Weights need not total 100. How it works
Use the Weighted Average Calculator
About the Weighted Average Calculator
A weighted average is Σ(value × weight) ÷ Σ weight: scores of 90, 85 and 95 with weights of 20, 30 and 50 average 91. This weighted average calculator takes up to 100 pairs of value and weight, shows how much each row adds to the result, and works with weights that do not total 100.
Course grade: scores of 90, 85 and 95 weighted 20, 30 and 50
| Item | Score | Weight | Share of weight | Contribution |
|---|---|---|---|---|
| Homework | 90 | 20 | 20% | 18 |
| Midterm | 85 | 30 | 30% | 25.5 |
| Final exam | 95 | 50 | 50% | 47.5 |
| Weighted average | 100 | 100% | 91 |
Contribution is score × weight ÷ total weight. The contributions add up to the weighted average.
Average price paid over three purchases
| Purchase | Price | Quantity (the weight) | Share of weight | Contribution |
|---|---|---|---|---|
| First | 10 | 100 | 28.5714% | 2.85714 |
| Second | 12.5 | 200 | 57.1429% | 7.14286 |
| Third | 9 | 50 | 14.2857% | 1.28571 |
| Weighted average | 350 | 100% | 11.2857 |
The plain average of the three prices is 10.5. The weighted figure is higher because most of the units were bought at 12.5.
Grade point average with credit hours as weights
| Course | Grade points | Credit hours | Share of weight | Contribution |
|---|---|---|---|---|
| Course 1 | 4 | 3 | 30% | 1.2 |
| Course 2 | 3 | 4 | 40% | 1.2 |
| Course 3 | 3.7 | 3 | 30% | 1.11 |
| Weighted average | 10 | 100% | 3.51 |
How to use this tool
- Type each value and its weight on one row. A weight can be a percentage, a number of credit hours, a quantity or any number that is not negative.
- Press Add Row for more pairs, up to 100.
- Read the weighted average, the total weight it was divided by, and the table of each row’s share and contribution.
Frequently asked questions
- How do you calculate a weighted average?
- Multiply each value by its weight, add the products and divide by the sum of the weights. For 88, 92, 76 and 85 weighted 15, 25, 20 and 40: (1320 + 2300 + 1520 + 3400) ÷ 100 = 85.4.
- Do the weights have to add up to 100?
- No. The sum of the products is divided by whatever the weights total, so only their proportions matter. Weights of 2, 3 and 1 on values of 80, 90 and 70 give 500 ÷ 6 = 83.3333. The tool states the total it used.
- How do I work out my grade so far when not everything is graded?
- Enter only the items that have a score. With 80 on work worth 40% and 90 on work worth 30%, the weights total 70 and the average so far is 5900 ÷ 70 = 84.2857.
- What is the difference between a weighted average and a normal average?
- A normal average gives every value the same weight. 90, 85 and 95 average 90 unweighted, and 91 when the weights are 20, 30 and 50, because the value with the largest weight pulls the result toward itself.
- How do I calculate a weighted average price?
- Use the quantity as the weight. Buying 10 shares at 20 and 30 shares at 30 costs (200 + 900) ÷ 40 = 27.5 a share on average, not the 25 that averaging the two prices would give.
- Can a weight be zero or negative?
- A weight of 0 is accepted: the row is counted but adds nothing to the result. A negative weight is rejected with a message, and if every weight is 0 there is nothing to divide by.
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