Weighted Average of a List Calculator
Average a list of numbers where each value carries its own weight — enter values and matching weights to get the true weighted mean.
How it works
Weighted average = Σ(value × weight) ÷ Σ(weight)
A weighted average lets some values count more than others — grades weighted by credit hours, prices weighted by quantity, ratings weighted by number of reviews. Each value is multiplied by its weight, the products are summed, and the total is divided by the sum of the weights. When every weight is equal the result collapses back to the ordinary mean, so the weighted average is a strict generalization of it.
Worked example
Scores 80, 90, 70 carry weights 2, 3, 1. Σ(value × weight) = 160 + 270 + 70 = 500. Σ(weight) = 6. Weighted average = 500 ÷ 6 = 83.33, higher than the plain mean of 80 because the 90 carries the most weight.
Sources: Weighted arithmetic mean — Wikipedia
Frequently asked questions
What if my values and weights have different lengths?
They must match one-to-one. The calculator reports the mismatch so you can fix a missing or extra number before trusting the result.
Do the weights have to add up to 1 or 100?
No. Any positive weights work — the division by their sum normalizes them automatically, so 2, 3, 1 gives the same answer as 0.333, 0.5, 0.167.
Can a weight be zero?
Yes, a zero weight simply drops that value from the average. But if every weight is zero the sum is zero and the weighted average is undefined.
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This calculator is for educational purposes. Double-check important results before acting on them.