The formula
Your course grade is a weighted average of the work done so far and the final exam:
Course grade = current grade × (1 − w) + final score × w
where w is the weight of the final as a decimal. Solving for the final score:
Score needed = (target − current × (1 − w)) ÷ w
Worked example
You have 84% in the class, the final is worth 30% of the grade and you want to finish with 85%.
- Work done so far counts for 70%: 84 × 0.70 = 58.8 points.
- Points still needed: 85 − 58.8 = 26.2.
- Score needed: 26.2 ÷ 0.30 = 87.3% on the final.
- With a perfect final, the best possible course grade is 88.8%.
- With a zero on the final, the course grade would drop to 58.8%.
So an A (90%) is out of reach this term, but a strong final keeps the B+.
What different targets require
With the same 84% and a final worth 30%:
| Target course grade | Score needed on the final |
|---|---|
| 90% (A) | 104% (not reachable) |
| 85% | 87.3% |
| 80% (B) | 70.7% |
| 70% (C) | 37.3% |
Tips for using it
- Use your actual weighted grade. If your teacher drops the lowest quiz or weights categories, use the current grade shown in your gradebook, not a simple average.
- Check the weight of the final in the syllabus. Some courses also have a minimum score on the final to pass.
- Points-based classes: if your grade is total points earned ÷ total points possible, the final’s weight is its points ÷ the course total.
- Plus and minus grades: many schools set B+ at 87%, A− at 90% or 93%; check your school’s scale.
Planning your study time
The higher the weight of the final, the more it can move your grade. When the needed score is low, a moderate effort is enough to secure the grade; when it is close to 100%, it may make sense to ask about extra credit or retakes early, before exam week.