Weighted Average Calculator
Enter value and weight pairs to compute the weighted average, weighted standard deviation and total weight, skipping any blank lines.
A weight can be credits, a rank, a share like 0.4 or a percentage like 40% — only how the weights compare to each other matters.
Weighted average: 90 Total weight: 6 Weighted std dev: 5 Plain mean (weights ignored): 88.333333 Valid pairs: 3
(90×3 + 80×1 + 95×2) / (3 + 1 + 2) = (270 + 80 + 190) / 6 = 540 / 6 = 90Result: 4 lines, 72 characters
Weighted average from value and weight pairs
Enter one value, weight pair per line and the tool computes the weighted average live as you type. The weighted mean is defined as sum(value × weight) / sum(weight), so values with larger weights pull the result toward them more strongly than lightly weighted ones. Alongside the average you also see the weighted standard deviation — how tightly the values cluster around that weighted mean — the total weight, and how many valid pairs were parsed, with a "Plain mean (weights ignored)" line so you can see what the weighting changed, and a "Worked out" block that writes the arithmetic with your numbers — the products, the two sums and the division. Blank lines are skipped, and a line missing a number is left out with a note saying how many were — so you can paste a rough list from a spreadsheet and still get a clean answer. Copy link hands the list to someone else without ever writing it into the address bar.
Where a weighted average is useful
Weighted averages show up whenever some items count for more than others: a course grade where the final exam is worth more than a quiz, a GPA where each class is weighted by credit hours, an investment return weighted by the amount held in each position, or a survey score weighted by the number of respondents. Enter each item's value and its weight, and the calculator gives the single number that fairly summarizes the whole set. If every weight is the same, the weighted average is identical to the ordinary mean.
Frequently asked questions
How is the weighted average calculated?
It multiplies each value by its weight, adds those products together, and divides by the sum of the weights: sum(value × weight) / sum(weight). For example, 90 with weight 3 and 80 with weight 1 gives (90×3 + 80×1) / (3 + 1) = 350 / 4 = 87.5.
What happens if the total weight is zero or a line is malformed?
A total weight of zero has no defined average, so the tool shows a prompt instead of a number. Lines that are blank, missing the second number, or contain non-numeric text are ignored, and only the valid value/weight pairs are used.
What is the weighted standard deviation shown below the average?
It measures how spread out the values are around the weighted mean, giving each point its weight: sqrt(sum(weight × (value − mean)²) / sum(weight)). A result of 0 means every value is identical; a larger number means the values are more dispersed.
Can the weights be percentages?
Yes. A weight can be credits, a rank, a share or a percentage written with a % sign. Only how the weights compare with each other matters, so they need not add up to any particular total.
Can I see the arithmetic, or how much the weights changed the answer?
Yes. A "Worked out" block writes the sum with your numbers — (70×2 + 80×3 + 90×1) / (2 + 3 + 1), then the products, the two sums and the answer — and for a long list only the totals, saying why. "Plain mean (weights ignored)" sits in the answer so the effect of the weighting is visible.