Weighted Average Calculator
How to calculate a weighted average
Enter each value with its weight, one pair per line. The calculator multiplies each value by its weight, adds those products, and divides by the total weight: Σ(value × weight) ÷ Σ(weight).
Worked example
Grades 90 (weight 3), 80 (weight 2), 70 (weight 1): (90×3 + 80×2 + 70×1) ÷ (3+2+1) = (270 + 160 + 70) ÷ 6 = 500 ÷ 6 = 83.33.
When is a weighted average used?
Course grades (exams worth more than homework), GPA with credit hours, portfolio returns, and any average where some items count more than others.
Frequently asked questions
A normal average treats every value equally. A weighted average multiplies each value by its importance (weight) first, so bigger weights pull the result toward their values.
Yes. Weights like 0.5 or 2.5 work fine, as long as the total weight is not zero.
No. The formula divides by the actual total weight, so any positive weights work, 3, 2, 1 or 30%, 20%, 10% both give the same answer.
The weighted average formula in full
Every weighted average follows the same two totals. Multiply each value by its weight and add those products to get the top total. Add the weights on their own to get the bottom total. Divide the first total by the second and you have the answer.
Weights written as percents and weights written as plain counts both work, as long as you use one style through the whole sum. A weight of 50% and a weight of 50 give the same result, because only the share of the total weight matters, not the scale you wrote it on.
Example: A course grade from three parts
Step 1, List the pairs: Homework scores 92 with weight 20, the midterm scores 84 with weight 30, and the final exam scores 78 with weight 50.
Step 2, Multiply and add: 92*20 + 84*30 + 78*50 = 1840 + 2520 + 3900 = 8260. The weights add to 20 + 30 + 50 = 100.
Step 3, Divide: 8260 / 100 = 82.6. The final course grade is 82.6, pulled toward the final exam because it carries half the total weight.
Common mistakes
- Averaging the averages: Adding 92, 84, and 78 and dividing by 3 gives 84.67, which ignores the weights and overstates this grade.
- Mixing weight styles: Using 20 for one weight and 0.30 for another in the same sum breaks the shares. Pick percents or decimals and convert them all.
- Forgetting the final division: The product total, 8260 in the example above, is not the average. You must still divide by the total weight.
How to check your result
A weighted average always falls between the smallest and the largest value you entered. If your answer sits outside that range, a weight or a product is wrong. It should also sit closer to the values with the biggest weights. In the example above, 82.6 sits between 78 and 92 and leans toward 78, exactly as a 50 percent final exam weight should make it lean.
More questions
No. A weighted average always lies between the lowest and highest values, inclusive. A result outside that range means an arithmetic error, usually a missed weight in the total.
That value drops out of the calculation completely. Its product is zero and it adds nothing to the total weight, so the average is set by the remaining values alone.
Convert them to one common scale before you average. Mixing a score out of 50 with a score out of 100 without converting first will distort the result, even with correct weights.