Compute a weighted mean from values and their weights
Enter your values above and a matching weight for each one below to get the weighted average. Weights can be percentages, decimals or whole numbers — only their relative size matters.
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A weighted average (or weighted mean) is an average in which some values count more than others. Instead of treating every value equally, each is multiplied by a weight that reflects its importance, and the results are combined. It is the right tool whenever the items being averaged do not contribute equally — course grades, portfolio returns, survey results, or prices across different quantities.
The weighted average is Σ(xᵢ × wᵢ) ÷ Σwᵢ: multiply each value by its weight, add those products, and divide by the sum of the weights. If all the weights are equal, the weighted average reduces to the ordinary (arithmetic) mean. The weights do not need to add up to 1 or 100 — the formula divides by their total, so only the ratios between them matter.
Suppose a course grade is 30% homework (90), 20% quizzes (85), 10% participation (80), 25% midterm (95) and 15% final (70). Multiplying each score by its weight and dividing by the total weight (1.0) gives a weighted average of 86.5 — higher than the simple average of 84, because the heavily weighted components scored well.
Multiply each value by its weight, add the products, and divide by the sum of the weights: Σ(value × weight) / Σ(weight).
No. The formula divides by the total of the weights, so only their relative sizes matter. Percentages, decimals and whole numbers all work.
A regular average treats every value equally. A weighted average lets some values count more, which is why it can differ from the simple mean.