Calculate a Weighted Average
This free weighted average calculator finds the mean of a set of values when each one counts for a different amount. Enter your values in one box and their matching weights in the other, and the tool above returns the weighted average instantly. Unlike a plain average, where every number counts equally, a weighted average reflects the fact that some items matter more — like an exam that is worth more than a quiz, or a large purchase that affects your budget more than a small one.
How to Use the Calculator
- Enter your values, comma separated (for example, 90, 80, 70).
- Enter the matching weights in the same order (for example, 0.5, 0.3, 0.2).
- Press Calculate to get the weighted average.
The weights can be decimals that add to 1, percentages, or any positive numbers — the calculator divides by the total weight, so you do not have to make them sum to anything in particular.
The Weighted Average Formula
Multiply each value by its weight, add those products together, then divide by the sum of the weights: Weighted average = ?(value x weight) / ?(weight). For example, with grades of 90, 80, and 70 weighted 50%, 30%, and 20%: (90 x 0.5 + 80 x 0.3 + 70 x 0.2) / (0.5 + 0.3 + 0.2) = (45 + 24 + 14) / 1 = 83. A plain average of those same grades would be 80, so the weighting matters.
Where Weighted Averages Matter Most
The classic use is school grades, where categories like homework, quizzes, midterms, and the final each carry a different percentage of the total. They are also central to finance (a portfolio’s return is the weighted average of its holdings), to business (average cost when you buy stock at different prices and quantities), and to surveys and reviews (a star rating weighted by the number of reviews). Any time “how many” or “how much” varies between items, the weighted average is the honest way to combine them.
Weighted Average vs. Simple Average
A simple average treats every value as equally important, which is fine when they are. But it gives misleading results when they are not — averaging a 95% on a 5% quiz with a 60% on a 60% final as if they were equal would badly misrepresent the grade. The weighted average fixes this by scaling each value by its importance. If you only need a plain mean, our average calculator is the simpler choice; for grades specifically, pair this with the final grade calculator.
Frequently Asked Questions
How do I calculate a weighted average?
Multiply each value by its weight, add the results, and divide by the total of the weights. The tool above does it instantly.
Do the weights need to add up to 100% or 1?
No. The calculator divides by the sum of the weights, so any positive weights work — percentages, decimals, or counts.
Is the weighted average calculator free?
Yes — free, browser-based, and no signup needed.
A Step-by-Step Example
Imagine a course graded as homework 20%, midterm 30%, and final 50%, with scores of 95, 80, and 88. Multiply each score by its weight: 95 × 0.20 = 19, 80 × 0.30 = 24, and 88 × 0.50 = 44. Add the products (19 + 24 + 44 = 87) and divide by the total weight (1.0) to get a weighted average of 87. A simple average of 95, 80, and 88 would be about 87.7 — close here, but the gap widens whenever the weights are uneven or the scores vary more. Entering the values and weights above gives you the exact figure without the manual arithmetic.
Where Weighting Changes the Outcome
Weighted averages matter most when the items differ greatly in importance. A 100% on a 5% quiz cannot rescue a 50% on a 60% final, and a weighted average makes that reality clear where a plain average would mislead. The same logic powers a stock portfolio’s return (each holding weighted by its size), a company’s average purchase cost across different order quantities, and an overall star rating weighted by the number of reviews. Any time “how much” or “how many” varies between the values you are combining, the weighted average is the accurate way to summarize them — and it is the foundation of how grade point averages are calculated.
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