Method 1: Weighted average of all work
Most courses split your grade into weighted parts — homework, quizzes, labs, a midterm, and a final. Multiply each part's score by its weight (as a decimal), add everything, and divide by the total weight.
Final grade = Σ(score × weight) ÷ Σ(weight)Example: Homework 90% (worth 20%), quizzes 84% (worth 20%), midterm 88% (worth 25%), final 85% (worth 35%). Grade = (90×0.2 + 84×0.2 + 88×0.25 + 85×0.35) ÷ 1 = 86.6%.
Method 2: Find what you need on the final
If you already know your grade before the final, use this formula to find the minimum final-exam score needed to reach your target:
Needed on final = (target − current × (1 − final weight)) ÷ final weightExample: You have 82% going into the final, the final is worth 30%, and you want 90%. Needed = (90 − 82×0.7) ÷ 0.3 = 108.7%. Since that is above 100, an A is out of reach — but to keep a B (85%), you need (85 − 57.4) ÷ 0.3 = 92%.
Common mistakes
Forgetting that the final's weight means the rest of your grade only counts for (100% − final weight). And check whether weights are percentages (must total ~100) or points.