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Weighted Final Exam Calculator
Tell it how much your final is worth and it does the weighting for you — the score you need, and exactly how far a great or terrible final can swing your grade.
Short answer
The final’s weight is the share of your grade it carries, and your current grade is locked in at whatever weight is left. A final worth 30% can move your grade three times as much as one worth 10%. Overall = current × (1 − weight) + final × weight, so an 85% going into a final worth 20% finishes somewhere between 68% (a zero) and 88% (a perfect score).
Why a heavier final cuts both ways
A final worth more of your grade is a bigger opportunity and a bigger risk at the same time. If you’re behind, weight is your friend — there’s more grade left to claw back. If you’re ahead, a heavy final can undo a strong semester, so a defensive score matters more. The range shown above is the honest picture: the wider it is, the more the final decides your grade.
How we calculate this
Your class grade is a weighted blend of the work you've done and the final exam. This tool applies that arithmetic exactly and solves it for the score you need:
- Split your grade into what's banked and what's left. If the final is worth 30% of your grade, everything else is worth the other 70%. Your current grade already reflects that 70%, so it's 'banked' — the final can only move the remaining 30%.
- Blend the two by the final's weight. Overall = current × (1 − weight) + final × weight. With an 88% going in and a final worth 30%, 88 × 0.70 = 61.6 points are locked in before you sit the exam.
- Solve for the score you need. Rearranged, needed final = (target − banked) ÷ weight. To reach a 90% overall from that 88%, you'd need (90 − 61.6) ÷ 0.30 = 94.7% on the final.
- Check it's actually reachable. If the answer is above 100%, the target is out of reach and the tool tells you the best you can still finish with. If it's zero or below, you've already secured the target — even a blank final keeps you there.
Assumptions
- Your 'current grade' already accounts for every graded item except the final, weighted the way your syllabus weights them. Read it off your course portal, not a hand-average.
- The final's weight is the share of your overall grade it carries — check the syllabus, since exams, homework, and participation are often weighted differently.
- Percentages assume percentage-based grading. If your class is scored in raw points, use the points-based calculator instead.
- Letter-grade and GPA conversions use the most common US scale with A+ capped at 4.0; your registrar's published scale is authoritative.
- Everything is computed in your browser. Nothing is uploaded or stored.
Sources
Last reviewed: July 18, 2026
How far a final can move an 85% grade
| Final is worth | If you ace it (100) | If you bomb it (50) |
|---|---|---|
| 10% | 86.5 | 81.5 |
| 20% | 88 | 78 |
| 30% | 89.5 | 74.5 |
| 40% | 91 | 71 |
| 50% | 92.5 | 67.5 |
The heavier the final, the more it can swing your grade — in both directions. Enter your own numbers above to see your exact range.
How does the weight of the final affect my grade?+
The weight is the share of your overall grade the final carries. A final worth 30% can move your grade three times as much as one worth 10%. Your current grade is locked in at whatever weight is left over, so a heavier final means more of your grade is still up for grabs.
My final is worth 20% — how much can it change my grade?+
At most 20 percentage points in either direction from what you'd get with a 50% final. Concretely, an 85% going into a final worth 20% finishes between 68% (a zero) and 88% (a perfect score). Enter your numbers to see your exact ceiling and floor.
How do I convert my final's weight to a decimal?+
Divide the percentage by 100: a final worth 25% is 0.25. The formula uses that decimal — overall = current × (1 − 0.25) + final × 0.25 — but you can just type the percentage here and the calculator converts it.
What if my final replaces my lowest test instead of having a weight?+
That's a different rule — some classes drop your lowest grade or let the final override it. This calculator handles the standard weighted-average case. If your syllabus uses a replacement rule, compute your grade both ways and take the better one.
Graded in raw points instead? Use the points-based final calculator, or see what your final does to your GPA.