Weighted Average Calculator
Find a weighted average, where each value counts in proportion to its weight: a course grade from assignments worth different percentages, an average price across quantities, or a score from weighted criteria.
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What do I need on the final exam?
Your average on everything except the final.
How do I calculate a weighted average?
Multiply each value by its weight, add the products, and divide by the sum of the weights. Scores of 80, 90 and 70 weighted 20%, 30% and 50% give 16 + 27 + 35 = 78. Weights don’t have to be percentages: 2, 3 and 5 give the same answer, because only their proportions matter.
- Enter each value and its weight on a row. Add rows for more values.
- Tick “Weights are percentages” if they should add up to 100, as for course grades; you’re warned if they don’t.
- Read the weighted average, the total weight and the plain average for comparison.
Formulas & Methods
Weighted average
Example: (80 × 20 + 90 × 30 + 70 × 50) ÷ 100 = 78
Same weights as plain numbers
Example: (80 × 2 + 90 × 3 + 70 × 5) ÷ 10 = 78
Score needed on the final
Example: 82 so far, final worth 30%, aiming for 85: (85 − 82 × 0.7) ÷ 0.3 = 92
Key features
Any kind of weight
Percentages, credits, quantities or points: the result is divided by the actual total, so the weights never have to be rescaled.
100% check
In percentage mode, a total other than 100% is flagged, because it usually means a missing or mistyped weight.
Plain average alongside
See how much the weighting changes the result compared with treating every value equally.
What you need on the final
Enter your grade so far, the final exam’s weight and the grade you want to see the score you need, or whether it is already secured or out of reach.
Negative values allowed
Values can be below zero, such as temperatures or returns; weights can be zero but not negative.
Common uses
- Work out a course grade from assignments worth different percentages
- Average prices bought in different quantities
- Score options on criteria that matter more or less
Finding a course grade so far
To see your grade before the final exam, enter only the assignments you have marks for, with their weights. If they are worth 60% of the course in total, the result is your average on that 60%. In percentage mode the calculator flags the 60% total as a reminder that some of the course is still to come.
Frequently Asked Questions
What is the difference between a weighted and a normal average?
A normal average treats every value equally. A weighted average lets some count more: a final exam worth 50% moves the result five times as much as a quiz worth 10%.
Do the weights have to add up to 100?
No. The sum of the products is divided by the total of the weights, whatever it is. Percentages are just weights that happen to total 100.
Why can the score needed be over 100%?
Because the target is out of reach: even a perfect final wouldn’t lift the course grade that far. With 60% so far and a final worth 20%, reaching 90% would need 210% on the final.
How do I do this in a spreadsheet?
Use =SUMPRODUCT(values, weights) / SUM(weights), with the values in one column and the weights in the next.
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