Weighted Average Calculator
Every value with its own weight, one pair on each line, and the answer with both sums printed. This page opens on a gradebook: 88 at a weight of 20, 92 at 30 and 79 at 50, which is 8470 divided by a total weight of 100, so the weighted mean is 84.7. Averaging the three marks and forgetting the weights gives about 86.3, and that is a different grade.
One pair on each line: the value first, then the weight it carries, separated by a space, a comma or a tab. Weights need not add up to 100: only their proportions matter, so 3 and 1 weigh exactly as 75 and 25 do. A line that does not hold two numbers is named rather than skipped.
| Value | Weight | Share of the total weight | Value × weight |
|---|---|---|---|
| 88 | 20 | 20% | 1760 |
| 92 | 30 | 30% | 2760 |
| 79 | 50 | 50% | 3950 |
Common questions
- How do you calculate a weighted average?
- Multiply each value by its weight, add those products up, then divide by the total of the weights. Here that is (88 × 20) + (92 × 30) + (79 × 50) = 8470, and 8470 ÷ 100 = 84.7. The tool prints that line in full, plus a table showing what each pair contributed and what share of the total weight it carried.
- How do I calculate my grade with weighted categories?
- Put each category's score on a line with the percentage it is worth: homework 88 at 20, midterm 92 at 30, final 79 at 50. The weights do not have to be percentages and they do not have to reach 100. Only their proportions matter, so 3 and 1 weigh exactly as 75 and 25 do, and the tool says what your weights added up to so a missing category is visible.
- Why is the weighted average lower than the plain average?
- Because the heaviest weight sat on the lowest value. The 79 carries half the total weight on this page, so it pulls the answer down to 84.7 while the unweighted mean of the same three marks is about 86.3. Whenever the two disagree, the row table shows which pair is doing it: the largest contribution beside the largest share.
- What if a weight is zero, or a line has only one number?
- A zero weight is allowed and simply contributes nothing, which is what an ungraded category should do. A line that does not hold exactly two numbers is refused by name, with the line number and what it says, rather than being skipped quietly: a dropped row changes the answer without changing anything you can see. If every weight is zero there is no average to give, and the tool says that instead of dividing by nothing.
- Can I get the mean, median and standard deviation too?
- Yes. Switch What to work out back to All statistics and paste a plain list of numbers: mean, median, mode, range, both standard deviations, the geometric and harmonic means, each with its working. For letter grades and credit hours rather than numbers and weights, the GPA calculator does the same arithmetic with the grade scale built in.
Exact for median, mode, minimum, maximum and range. The mean, variances and standard deviations use compensated summation and are accurate to roughly 15 significant digits, not claimed as exact, because double-precision arithmetic is not.