Find an average where some numbers count for more than others. Enter your numbers, and a matching weight for each one.
Each value is multiplied by its own weight.
Those products are added together.
The total is divided by the sum of the weights, not by the number of items.
When every weight is equal, the result is the same as a plain average.
Weighted average: Σ(value × weight) ÷ Σ(weight)
Σ: The sum across all items
A student scores 80 in a 4-credit subject and 60 in a 2-credit subject.
Values: 80, 60
Weights (credits): 4, 2
Multiply each: (80 × 4) + (60 × 2) = 320 + 120 = 440
Add the weights: 4 + 2 = 6
Divide: 440 ÷ 6 = 73.33
Answer: 73.33 (the plain average would have been 70)
When should I use a weighted average instead of a normal one?
Whenever the items are not equally important. Course marks weighted by credit hours, investment returns weighted by amount invested, and survey results weighted by group size all need a weighted average.
Do the weights have to add up to 100?
No. The formula divides by the total weight, so any consistent scale works — credits, rupees, percentages, or plain counts.
What if a weight is zero?
That value is left out of the average, which is the mathematically correct result.