Weighted Average Calculator
When Not Every Number Counts Equally
A plain average treats every value the same, but that's often the wrong model — a final exam usually counts for more of a course grade than a single homework assignment, and a large position in a portfolio moves its overall return more than a small one. A weighted average fixes this by multiplying each value by its relative importance before combining them, so bigger weights pull the result harder toward themselves.
The Formula
Every value/weight pair is multiplied together and summed, then divided by the sum of the weights alone — not by the number of items. Weights cannot be negative, and at least one value/weight pair is required.
Where Weighted Averages Are Used
- Grading — combining assignments, exams, and participation scores where each category has a different percentage weight.
- Investment portfolios — calculating an overall return or cost basis when position sizes differ.
- Survey and index calculations — combining responses or metrics where some carry more significance than others.
- Manufacturing quality metrics — combining defect rates across production batches of different sizes.
| Values & Weights | Weighted Average |
|---|---|
| 85 (0.3), 90 (0.3), 78 (0.4) | 83.7 |
| 100 (2), 150 (3), 200 (5) | 165 |
In the grading example, weights of 0.3, 0.3, and 0.4 sum to 1.0, so they can be read directly as percentages of the final grade.
How to Use This Calculator
- Enter Value 1 and Weight 1.
- Enter Value 2 and Weight 2.
- Optionally add up to three more value/weight pairs (Value 3–5, Weight 3–5).
- Select Calculate to see the weighted average.
Related Calculations
Need a straightforward proportional comparison instead? See the Percentage Calculator, or the Ratio Calculator for simplifying and solving proportional relationships.