The final exam formula
You need three numbers: your current grade (C), how much the final is worth (F, as a decimal — 20% = 0.20), and your target course grade (T).
This assumes your current grade already covers everything except the final. If some coursework is still ungraded, use the grade calculator with the “What do I need on the final?” tab and enter the exact weights.
Worked examples
1. Aiming for a B
Current grade 85%, final worth 20%, target 80%:
(80 − 85 × 0.80) ÷ 0.20 = (80 − 68) ÷ 0.20 = 60% on the final.
2. Aiming for an A
Same class, target 90%: (90 − 68) ÷ 0.20 = 110%. Above 100%, so an A isn’t reachable without extra credit or a curve.
3. A heavier final
Current grade 78%, final worth 30%, target 80%: (80 − 78 × 0.70) ÷ 0.30 = (80 − 54.6) ÷ 0.30 ≈ 84.7%.
Quick chart: final worth 25%
Find your current grade on the left to see the minimum final score for each target.
| Current grade | Need for 90% (A−) | Need for 80% (B−) | Need for 70% (C−) |
|---|---|---|---|
| 95% | 75% | 35% | 0% (already locked in) |
| 92% | 84% | 44% | 4% |
| 90% | 90% | 50% | 10% |
| 88% | 96% | 56% | 16% |
| 85% | 105% (not possible) | 65% | 25% |
| 82% | 114% (not possible) | 74% | 34% |
| 80% | 120% (not possible) | 80% | 40% |
| 75% | 135% (not possible) | 95% | 55% |
| 70% | 150% (not possible) | 110% (not possible) | 70% |
How to use this during finals week
- Grab your current grade from your school portal (make sure every graded item is in).
- Check the syllabus for the exact weight of the final.
- Run the formula — or let the calculator do it — for two targets: the grade you want and the one you need.
- Spend study time where it moves the needle: a final worth 30%+ deserves priority.
FAQ
What if I need more than 100% on the final?
Then that target isn’t reachable from the final alone. Ask whether there’s extra credit, a curve, or a dropped score — or aim for the next grade down.
What does a negative number mean?
You’ve already secured that grade — even a 0 on the final keeps you at or above the target (assuming the weights are correct).
Does this work if the final replaces my lowest test?
Not directly. Replacement policies change the weights. Recalculate your current grade as if the final score replaced the lowest test, then compare.
Is my current grade the same as my portal grade?
Usually, if the portal already weights categories. Some portals show a points-only average — check the syllabus weighting first.
Related
Let the calculator do the math.
Calculate my final grade →