Weighted average calculator
Type each value with its weight as value:weight, separated by commas or new lines, for example 90:30, 80:20, 70:50. You get the weighted average, the total weight, the sum of value times weight and the plain average.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Write each value followed by a colon and its weight.
- Separate pairs with commas, semicolons or new lines. A space or the letter x also works between value and weight.
- Read the weighted average and compare it with the plain average.
How it works
Weighted average = Σ(value × weight) / Σ(weight). Negative weights are rejected and the total weight must be above zero. Results show up to 12 significant digits.
Worked example
Scores 90, 80 and 70 with weights 30, 20 and 50:
- 90 × 30 + 80 × 20 + 70 × 50 = 2700 + 1600 + 3500 = 7800
- Total weight: 100
- Weighted average: 7800 / 100 = 78
Tips
- For course grades, use credits or the percentage of the final mark as weights.
- A weight of 0 leaves that value out of the result.
- Check that the weights are all in the same unit: mixing 0.3 and 20 skews the answer.
Frequently asked questions
What is a weighted average?
An average where some values count more than others. Each value is multiplied by its weight, the products are added, and the total is divided by the sum of the weights.
How do I calculate a weighted grade?
Enter each score with its weight, for example 90:30, 80:20, 70:50 for a 30%, 20% and 50% split. The result is (90 × 30 + 80 × 20 + 70 × 50) / 100 = 78.
Do the weights have to add up to 100?
No. The calculator divides by the total weight, so credits, hours or counts work as they are. Percent weights that add up to 100 give the same answer as dividing by 100.
Why is the weighted average different from the plain average?
The plain average treats every value equally. In the example the plain average is 80, but the heavily weighted 70 pulls the weighted average down to 78.