How it works
A weighted average gives some values more influence than others. Each value is multiplied by its weight, the products are added, and the total is divided by the sum of the weights.
A common use is course grades: if homework is 30% of the grade at 90, a midterm 20% at 85 and the final 50% at 78, the weighted average is (90 × 30 + 85 × 20 + 78 × 50) ÷ 100 = 83.
Weights do not need to add to 100. Credit hours, quantities purchased or any positive numbers work, because the result is always divided by the total weight.
Formula
Weighted average = Σ(wᵢ × xᵢ) ÷ Σwᵢ
Questions people ask
Do my weights have to add up to 100%?
No. The formula divides by the total weight, so weights of 3, 2 and 5 give the same answer as 30%, 20% and 50%.
How do I calculate GPA with credit hours?
Enter each course’s grade points (such as 4.0 for an A) as the value and its credit hours as the weight. The weighted average is your GPA.
How is this different from a simple average?
A simple average treats every value equally. The weighted average equals the simple average only when all weights are the same.