Weighted Average Calculator
MathAdd values and their weights — grades and percentages, prices and quantities, scores and credits — and get the weighted average with the working shown.
Last updated: October 2026
A weighted average gives some values more influence than others. Each value is multiplied by its weight, the products are added up, and the total is divided by the sum of the weights. When every weight is the same, it equals the ordinary average. You need one whenever items don't count equally. A final exam worth 50% of a course grade counts more than homework worth 20%. A stock bought as 300 shares counts more toward your average cost than 50 shares bought later. A product's average selling price depends on how many units sold at each price. Weights can be percentages, credits, quantities or any other positive numbers — they don't have to add up to 100. This weighted average calculator divides by whatever total you enter, and also shows the simple average so you can see how much the weighting changes the result.
How to Calculate a Weighted Average
1. List each value with its weight (e.g. score 78, weight 30%). 2. Multiply each value by its weight. 3. Add up all those products. 4. Add up all the weights. 5. Divide the sum of products by the sum of weights.
Formula
Weighted average = Σ (xᵢ × wᵢ) ÷ Σ wᵢ xᵢ — each value (score, price, rate…) wᵢ — its weight (percentage, credits, quantity…) If the weights already sum to 1 (or 100%), the division just undoes the scaling.
Weighted Average Examples
Example 1 — Course grade (default inputs)
Homework 92 × 20 = 1,840 Midterm 78 × 30 = 2,340 Final 85 × 50 = 4,250 Σ = 8,430 ÷ Σ weights 100 = 84.3 (Simple average of the three scores: 85.0)
Example 2 — Average cost per share
300 shares at $42.00 → 12,600 50 shares at $55.00 → 2,750 Σ = 15,350 ÷ 350 shares = $43.86 average cost per share
Example 3 — GPA with credit hours as weights
A (4.0) × 4 credits = 16.0 B (3.0) × 3 credits = 9.0 C (2.0) × 2 credits = 4.0 Σ = 29.0 ÷ 9 credits = 3.22
Getting Weighted Averages Right
- › Weights do not have to sum to 100. 2:1:1 works the same as 50%:25%:25%.
- › Use quantities, not prices, as weights when averaging prices: the weight is how much was bought or sold at each price.
- › A weighted average of percentages needs the right base. To average conversion rates across pages, weight each rate by its visitors, not equally.
- › Working out what score you need on a final? Enter the grades so far, add the final with its weight, and adjust its value until the average hits your target.