Categories and weights
In a weighted grade, the course is split into categories, and each category counts for a share of the final grade. A syllabus might say homework is 20%, quizzes 30% and tests 50%. A category with a higher weight moves the final grade more, even if it has fewer assignments.
A worked example
Suppose a student has a 95% average in homework, 82% in quizzes and 76% on tests. Multiply each average by its weight and add the results.
The weighted grade is 81.6%.
- Homework: 95 × 0.20 = 19.0
- Quizzes: 82 × 0.30 = 24.6
- Tests: 76 × 0.50 = 38.0
- Total: 19.0 + 24.6 + 38.0 = 81.6
When weights do not add up to 100
If the weights add up to more or less than 100, divide the weighted sum by the total of the weights you have. If the weights are 20, 30 and 40 (a total of 90), compute each category times its weight, add them, and divide by 0.90.
The same idea handles a category with no grades yet. Using the example above with no quiz scores: 19.0 + 38.0 = 57.0, and the weights in use total 70% (0.70), so the grade so far is 57.0 ÷ 0.70 = 81.4%. Check how your teacher handles empty categories, because some count them as zero.
Common mistakes
Most errors come from the setup rather than the arithmetic.
- Averaging the category percentages without weights. The plain average of 95, 82 and 76 is 84.3%, which is not the weighted result of 81.6%.
- Mixing points and percents. Convert each category to a percent first, or use total points within a category.
- Typing a weight as 20 in one place and 0.20 in another.
- Counting an ungraded category as zero when the teacher leaves it out, or the reverse.
Have a correction or a suggestion? Tell the studio.