How to Calculate a Weighted Average

A weighted average is useful when some tests, assignments or subjects count more than others. Instead of giving every result equal influence, each value is multiplied by its weight.

Weighted average formula

Weighted average = Σ(value × weight) ÷ Σ(weights)

Example with two tests

Suppose a test score is 80 with weight 40%, and another is 90 with weight 60%. The weighted result is (80 × 0.40) + (90 × 0.60) = 86.

Marks with different maximum scores

If the final result is based directly on raw marks, you often do not need a weighted-average formula. Add the marks obtained, add the maximum marks, then calculate the percentage. This naturally gives a 100-mark paper more influence than a 50-mark paper.

Weights and credits are not always the same thing

Universities may use credit hours, grade points or assessment percentages. A GPA calculation may therefore use grade point × credits, while an exam may use assessment weights. Always follow the official scheme for the final reported result.

Weighted average vs simple average

A simple average gives every value equal weight. If you average 60 and 90, the result is 75. If the second result counts twice as much, the weighted result is higher because the second score has greater influence.

Common mistakes

Using weights that do not add to 100% when they should.
Mixing raw marks with percentages without defining the weight system.
Using an equal average when the official assessment has different weights.
Rounding every component before calculating the final value.