BCBetter Calculators

Weighted Average Calculator

Calculate the weighted average of two values based on their relative weights.

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Enter your values and click Calculate

How It Works

The calculator multiplies each value by its corresponding weight, sums those products, then divides the total by the sum of all weights: weighted average = (value1 × weight1 + value2 × weight2) ÷ (weight1 + weight2). Dividing by the actual total weight — rather than assuming 1 or 100 — ensures correct proportional results even when weights are arbitrary numbers like dollar amounts, item counts, or population sizes. If the weights sum to 1, the formula is the classic weighted mean. If they sum to 100, the denominator effectively normalizes to percentages. For unequal or unusual weight totals, the division still yields the correct proportional average. A weight of zero causes that value to be excluded entirely from the result, which is useful when one component has not yet been scored or counted.

Examples

Class Grades
A midterm is an 80 (40% weight) and the final is a 90 (60% weight).
Result: The final weighted average is 86.
Investment Portfolio
A stock returned 10% (invested $5000) and a bond returned 4% (invested $2000). Using the dollar amounts as weights.
Result: The weighted average return is 8.2857%.
Using Percentages as Weights
Using whole numbers like 30 and 70 for weights instead of decimals.
Result: The weighted average is 82, and the total weight is 100.

Frequently Asked Questions

Do my weights have to add up to 1 or 100?
No. The calculator automatically divides by the total sum of the weights you provide. However, using decimals that sum to 1 or percentages that sum to 100 is the standard practice.
What is the difference between an average and a weighted average?
A standard average treats every number equally. A weighted average gives more importance (weight) to certain numbers over others.
Can I use dollar amounts as weights?
Yes! This is common in finance. You can input the principal amounts as the weights and the interest rates as the values to find the blended interest rate.
What happens if a weight is zero?
If a weight is exactly zero, its corresponding value is entirely ignored in the final calculation.

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