Weighted Average Calculator
Compute the weighted average of values with custom weights — ideal for college marks, grades and exam scores.
Comma-separated, e.g. 3, 4, 5.
One weight per value, e.g. 1, 2, 3.
Weighted average
4.3333
Total weight
6
Weighted sum
26
Count
3 values
Weights must match values
Weighted average = sum of (value × weight) ÷ total weight. It is used when some values matter more than others, such as marks with different credit weights.
Last updated: January 2026
How this calculator is verified
Checked by True Calculator automated test suite on
- Formula verified against a published worked example in the automated test suite
- Edge cases (zero, negative, boundary and unit-mismatch inputs) covered by unit tests
The full verification method is on our how we verify page. Found an error? Tell us and we will re-check it.
When to Use This Calculator
Use the weighted average calculator whenever some values should count more than others — exam marks weighted by subject importance, semester grades weighted by credits, share prices averaged by quantity bought, or rent splits weighted by room sizes. Indian students use it constantly, since CBSE and university results are weighted averages across subjects and semesters, and this calculator reproduces exactly the numbers on their mark sheets. Investors tracking the average price of a stock bought in several lots get the true cost basis because each lot counts by its size, and teachers build weighted internal-assessment marks in seconds. Portfolio and statistics learners verify textbook examples without spreadsheets. Because both values and weights are entered as plain comma-separated lists, any weighted-average problem reduces to two quick inputs.
How to Use This Calculator
- Step 1: Type the values in the values box, comma-separated, such as 80, 90, 70.
- Step 2: Type the matching weights in the weights box, comma-separated — 2, 3, 1 for marks weighted by importance.
- Step 3: Check both lists have the same length, since each value pairs with its own weight.
- Step 4: Read the weighted average, the total weight and the weighted sum from the result cards.
Worked Example
A class 10 student in Delhi scores 80 in Hindi, 90 in Maths and 70 in Science, with weights 2, 3 and 1 matching the board's emphasis. Entering values 80, 90, 70 with weights 2, 3, 1 gives a weighted average of 83.33 — the weighted sum of 500 divided by the total weight of 6. The plain average of 80 hides how heavily Maths counts. With equal weights of 1 and 1, scores 90 and 75 average to 82.5, and values 5, 10, 15 with weights 1, 2, 2 average to 11.
Tips and Common Mistakes
- •Tip 1: Use weights that add to a meaningful total like 100 or the credit count, so the weighted sum reads naturally.
- •Tip 2: Equal weights make the weighted average equal to the plain average — a quick sanity check for your entries.
- •Tip 3: Check the total weight card; if it comes out 0, no weights were recognised and the result is refused.
- ✗Mistake 1: Entering lists of different lengths — the calculator rejects them, and padding would silently distort the result.
- ✗Mistake 2: Using negative weights; they are invalid, and the calculator returns a hint instead of a misleading number.
Frequently Asked Questions
What is a weighted average?
A weighted average multiplies each value by its weight, sums these products, and divides by the total weight. It is used when some values matter more than others, such as marks where assignments carry different weight than exams.
How do Indian students use weighted averages for grades?
Under the CBSE and many state boards, internal assessment and theory carry different weightage — for example 30% and 70%. Multiplying each score by its weightage and dividing by 100 gives the final subject score, which the calculator does in seconds.
What should I do if my values and weights are different in number?
Every value needs exactly one weight. If the lists have different lengths the calculator shows a hint asking you to fix the input, so the result is never silently wrong.
Can weights be zero or negative?
Weights should be zero or positive — a negative weight has no real meaning and the calculator rejects it. A weight of zero simply removes that value from the average, which can be useful when excluding an item.
What happens if all weights are zero?
Dividing by a total weight of zero is undefined, so the calculator returns a hint instead of a number. Give at least one positive weight to get a valid weighted average.
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