WAvgLab

Weighted Average Calculator

Give each value its own weight.

value:weight pairs (comma-separated)

Example: 90:3, 80:2, 75:1

Weighted average

84.167

What you entered

Pairs: 3

1
Multiply each value by its weight, then sum
90×3 + 80×2 + 75×1= 505
2
Sum the weights
3 + 2 + 1= 6
3
Divide the weighted sum by the total weight
505 ÷ 6= 84.1667

Result

Weighted average: 84.167

The weighted average is 84.167 — values with larger weights pull the average more strongly toward themselves than a plain average would.

Weighted vs plain average for typical grade and portfolio splits

Paste the pairs from the second column into the input box exactly as written, in value:weight form. The last column shows what a plain unweighted average of the same values would have given, which is the gap the weighting is there to capture.

Scenario	Pairs to enter	Weighted average	Plain average
Calculator default	90:3, 80:2, 75:1	84.167	81.667
Homework 20, midterm 30, final 50	95:20, 78:30, 85:50	84.9	86
Homework 10, quizzes 25, exams 65	92:10, 84:25, 76:65	79.6	84
Final-heavy course	70:40, 85:30, 90:30	80.5	81.667
GPA over a 3-credit A and a 4-credit B	4:3, 3:4	3.429	3.5
One test worth 25%, one worth 75%	100:1, 50:3	62.5	75
Portfolio returns by allocation	8:60, 4:30, 2:10	6.2	4.667
Survey ratings by respondent count	4.5:120, 3.8:80, 4.2:50	4.216	4.167

Weights do not have to add to 100. Only their ratio matters, so 20, 30, 50 and 0.2, 0.3, 0.5 give the same answer. Grades shown here are illustrative: check your own syllabus for the exact weights and for any dropped-lowest-score or curve rules the calculation cannot see.

Not every value counts equally

A plain average treats every number the same, but a weighted average lets some values count more — a final exam worth 40% of a grade should influence the result more than a 5%-weighted quiz.

Common uses

Course grades, portfolio returns weighted by investment size, and survey results weighted by sample representativeness all rely on this same calculation.

Frequently asked questions

My course has: Homework 20%, Midterm 30%, Final 50%. I got 95, 78, 85. What's my grade?

Weighted average = (95×0.20) + (78×0.30) + (85×0.50) = 19 + 23.4 + 42.5 = 84.9. Without weights, the simple average would be 86 — the weighting shifts the result because your lowest score (midterm) carries more weight than homework.

How is weighted average different from a regular average?

A regular average treats every value equally. A weighted average lets some values count more. Use regular when all items matter equally (5 quiz scores). Use weighted when items have different importance (grades with different credit weights, portfolio holdings of different sizes).

How do I calculate a weighted GPA?

Multiply each course grade by its credit hours, sum the products, then divide by total credit hours. Example: A (4.0) in a 3-credit course + B (3.0) in a 4-credit course = (4×3 + 3×4) / (3+4) = 24/7 = 3.43 GPA.