Calculate a weighted average from values and their weights.
Calculated instantly in your browser.
How do you calculate a weighted average?
Weighted average = Σ(value × weight) ÷ Σ(weights). Each value is multiplied by its weight, the results are added, and the total is divided by the sum of the weights, so heavier weights pull the average toward their values. For example, values 80, 90, 70 with weights 1, 2, 1 give (80 + 180 + 70) ÷ 4 = 82.5.
Understanding your result
Each value is multiplied by its weight, the results are added, and the total is divided by the sum of the weights — so heavier weights pull the average toward their values.
Formula and method
Weighted average = Σ(value × weight) ÷ Σ(weights).
Assumptions and limitations
This tool multiplies each value by its weight and divides by the total weight, so weights may use any positive scale and need not sum to 100. The result is undefined when every weight is zero, since nothing remains to divide by. Negative weights fall outside the intended use and can produce misleading averages.
Worked example
Values 80, 90, 70 with weights 1, 2, 1 give (80 + 180 + 70) ÷ 4 = 82.5.
How to use this tool
- Enter your values.
- Enter a weight for each value, in the same order.
- Read the weighted average.
Common mistakes to avoid
- Entering a different number of values and weights.
- Using weights that are all zero.
About the Weighted Average Calculator
The Weighted Average Calculator finds the mean of a set of values where some count more than others. Enter each value and its weight to get the weighted average, plus the simple average for comparison.
Who should use this tool
Students working out weighted grades, and anyone averaging numbers that have different importance.
Benefits
- Handle values that carry different weights.
- See the simple average alongside the weighted one.
- Accepts comma or line-separated input.
- Private and instant — no sign-up.
Practical use cases
- Calculating a weighted course grade.
- Averaging review scores with different weights.
- Blending prices or rates by quantity.
Frequently asked questions
How is it different from a simple average?
A simple average treats every value equally; a weighted average lets some values count more, according to their weights.
Do the weights need to add up to 100?
No. Weights can be any positive numbers; the formula divides by their total, so percentages, counts or ratios all work.
Can I use weights that don't add up to 100?
Yes. The calculation divides the weighted total by the sum of the weights, so only the relative sizes matter, not their total. Weights of 1, 2 and 1 give the same result as 25, 50 and 25. Use whatever scale is natural for your data, such as credit hours or units sold.