The weighted grade formula
If each category i has score Si (as a percent) and weight Wi (as a percent of the course):
Course % = Σ (Si × Wi) ÷ Σ Wi
When weights already add to 100%, this is the same as Σ (Si × Wi / 100).
Worked example
| Category | Weight | Score | Contribution |
|---|---|---|---|
| Homework | 20% | 95% | 19.00 |
| Quizzes | 15% | 88% | 13.20 |
| Midterm | 25% | 82% | 20.50 |
| Projects | 15% | 91% | 13.65 |
| Final | 25% | — | (pending) |
Work so far (75% of the course): (19 + 13.2 + 20.5 + 13.65) = 66.35 points out of 75 → current average ≈ 88.47% on completed work.
What do I need on the final?
Let C = current average on weight Wc, Wf = final weight, T = target course %.
Needed on final = (T × (Wc + Wf) − C × Wc) ÷ Wf
Example: current 88.47% over 75%, final worth 25%, target 90%:
Needed = (90 × 100 − 88.47 × 75) ÷ 25 ≈ 94.6% on the final.
Tips
- Copy weights straight from the syllabus — typos here are the #1 error.
- If a category is incomplete, either omit it or estimate carefully.
- Some classes drop the lowest quiz; recalculate that category before weighting.
- Use our free grade calculator to avoid hand math during finals week.
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