When some numbers count more
A weighted average lets certain values pull harder on the result than others. Course grades, portfolio returns, and survey scores all work this way — a final exam worth half the grade should move your average more than a quiz worth a tenth. Enter your values and a matching list of weights to get the properly weighted result.
The formula
Multiply each value by its weight, add those products, then divide by the sum of the weights. Weights need not add up to 1; the division by their total normalizes them automatically, so 50, 30, 20 works just as well as 0.5, 0.3, 0.2.
Weighted versus simple mean
A simple mean treats every value equally — it is the special case where all weights are the same. This tool also shows that plain average alongside the weighted one, so you can see how much the weighting shifts the answer.
Related tools
For the three plain averages, use the mean median mode calculator; to measure spread, the standard deviation calculator.
Worked example
Scores 90, 80, 70 weighted 0.5, 0.3, 0.2 give (45 + 24 + 14) divided by 1 = 83 — higher than the simple mean of 80, because the strongest score carries the most weight.
FAQ
Do my weights have to sum to 1?
No. Any positive weights work; the calculator divides by their total, so only the relative sizes matter.
What if I have more values than weights?
The two lists must be the same length so each value pairs with one weight. The calculator flags a mismatch.