How to Calculate Your Grade With Weights (Step-by-Step)
Learn the exact formula for weighted grade averages. Worked examples with homework, quizzes, and exams — plus how to handle weights that don't add to 100%.
The weighted average formula
A weighted grade is just an average where some scores count more than others. The formula is:
Grade = (S₁ × W₁ + S₂ × W₂ + … + Sₙ × Wₙ) / (W₁ + W₂ + … + Wₙ)where Sᵢ is your percentage in category i and Wᵢ is its weight. If your weights already add to 100, the denominator is 100 and you can skip the division.
Step-by-step example
Suppose your syllabus says:
- Homework — 20%
- Quizzes — 20%
- Midterm — 25%
- Final exam — 35%
And your current scores are 88, 92, 78, and 85.
- Multiply each score by its weight: 88×0.20 = 17.6, 92×0.20 = 18.4, 78×0.25 = 19.5, 85×0.35 = 29.75.
- Add them: 17.6 + 18.4 + 19.5 + 29.75 = 85.25.
- Because the weights already total 100%, you're done — your weighted grade is 85.25%.
When weights don't add to 100
Real syllabi sometimes leave gaps (participation "up to 5%", extra credit, dropped categories). Just add the actual weights and divide by that total.
Example: weights of 20, 20, 25, 35, and a 5-point participation category worth 4% add to 104. If participation is 100, the numerator becomes 85.25 + 4 = 89.25, and the weighted average is 89.25 / 1.04 ≈ 85.82%.
Common mistakes
- Using raw points instead of percentages. Convert to a percent per category first.
- Forgetting to divide when weights don't sum to 100.
- Mixing decimals and percents — pick one (0.20 or 20) and stay consistent.
Skip the arithmetic
Our weighted average calculator handles all of this automatically, and the semester grade calculator projects your final grade from category weights. If you know your target grade, the final grade calculator tells you what you need on the last exam.