A weighted average lets some numbers count more than others. Course grades weight exams more heavily than homework, a portfolio’s return weights each holding by the money invested in it, and an average price per unit weights each price by the quantity bought. Enter the values and their weights and this calculator returns the weighted mean, along with a table showing exactly how much each value contributes.
How to use the weighted average calculator
- In Values (x), put one value per line — scores, prices, returns or ratings.
- In Weights (w), put the matching weight on the same line number. Percentages, credit hours, quantities or any other non-negative numbers work.
- Read the weighted average on the tape. The table below shows each weight’s share of the total and how many points that value adds to the result.
Both lists must have the same number of entries. You can paste two spreadsheet columns, one into each box.
Weighted average formula
Multiply each value by its weight, add the products, and divide by the sum of the weights. When the weights already add up to 1 (or 100%), the division simply converts back to the original scale.
Worked example
A course grade is made of four parts:
| Part | Score (x) | Weight (w) | w × x |
|---|---|---|---|
| Homework | 90 | 20 | 1,800 |
| Quizzes | 82 | 30 | 2,460 |
| Exams | 76 | 40 | 3,040 |
| Project | 95 | 10 | 950 |
| Total | 100 | 8,250 |
Weighted average = 8,250 ÷ 100 = 82.5.
The plain average of the four scores is (90 + 82 + 76 + 95) ÷ 4 = 85.75. The weighted result is 3.25 points lower because the weakest score, the exams, carries the largest weight. The contribution column on the tape makes this visible: exams add 30.4 points to the average while the project adds only 9.5.
Common uses
Grades and GPA
Syllabi usually list category weights that add to 100%. Enter category averages as values and the percentages as weights, or let the grade calculator do it with named categories and a target grade. For a grade point average, where each course is weighted by credit hours, use the GPA calculator.
Prices and inventory
If you buy 100 units at $4.00, 300 at $3.50 and 50 at $5.00, the average cost per unit is (400 + 1,050 + 250) ÷ 450 ≈ $3.78, not the simple average of the three prices, $4.17. Accountants call this weighted-average cost.
Survey and index data
Pollsters weight responses so a sample’s mix of ages, regions and other traits matches the population, and price indexes such as the Bureau of Labor Statistics’ Consumer Price Index weight each category by its share of consumer spending.
Common mistakes
- Averaging averages. Two class sections averaging 80 (30 students) and 90 (10 students) do not average 85 overall. Weighted by size, the combined average is (80 × 30 + 90 × 10) ÷ 40 = 82.5.
- Mismatched order. Each weight must line up with its value. If the lists are off by one line, every pairing is wrong.
- Missing categories. If your weights add to less than 100% because some work is not graded yet, the result is your average so far — which is often exactly what you want to know.
Frequently asked questions
Do the weights have to add up to 100?
No. The formula divides by the total weight, so weights of 20, 30, 40 and 10 give the same answer as 0.2, 0.3, 0.4 and 0.1, or as 2, 3, 4 and 1. Only the proportions between the weights matter.
How is a weighted average different from a regular average?
A regular (arithmetic) mean gives every value the same weight. A weighted average lets some values count more than others, so a final exam worth 40% of a grade moves the result four times as much as a quiz worth 10%.
How do I calculate a weighted average in Excel or Google Sheets?
Put values in one column and weights in another, then use =SUMPRODUCT(values, weights)/SUM(weights). That is exactly the formula this calculator applies.
Can a weight be zero?
Yes. A value with weight 0 is ignored. Weights cannot be negative, and at least one weight must be greater than zero.
Is GPA a weighted average?
Yes. A GPA weights each course's grade points by its credit hours. The GPA calculator handles the letter-grade conversion for you.