The formula
Your course grade is a weighted average of the work done so far and the final exam. If the final is worth w percent, everything else is worth (100 − w) percent:
course grade = current × (1 − w) + final × w
Rearranging for the final exam score gives the number this calculator reports:
final needed = (target − current × (1 − w)) ÷ w
Here w is written as a decimal (25% = 0.25), and "current" is your grade on everything except the final, as shown in your course portal or worked out from your marks.
Worked example
You have 82% going into the final, the final is worth 25%, and you want at least 80% overall (the default values above).
- The work done so far contributes 82 × 0.75 = 61.5 points.
- You need 80 − 61.5 = 18.5 more points from the final.
- The final is worth 0.25, so you need 18.5 ÷ 0.25 = 74% on the exam.
Check: 61.5 + 74 × 0.25 = 61.5 + 18.5 = 80. The same student would finish on 61.5% with a zero on the final and on 86.5% with a perfect final, so any grade outside that range is out of reach.
What you need for each letter grade
| Target | Calculation | Final exam score needed |
|---|---|---|
| A (90%) | (90 − 61.5) ÷ 0.25 | 114% – not possible |
| B (80%) | (80 − 61.5) ÷ 0.25 | 74% |
| C (70%) | (70 − 61.5) ÷ 0.25 | 34% |
| D (60%) | (60 − 61.5) ÷ 0.25 | below 0% – already secured |
The 90/80/70/60 cut-offs are common in US schools but not universal. Many courses use plus and minus grades, curves or different boundaries, and universities in other countries use their own scales, so set the target to your syllabus's cut-off.
How much the weight matters
The heavier the final, the more it can move your grade, in both directions. Three students who all want 80%:
| Current grade | Final weight | Score needed |
|---|---|---|
| 85% | 30% | (80 − 59.5) ÷ 0.3 = 68.3% (an A would need 101.7%) |
| 74% | 40% | (80 − 44.4) ÷ 0.4 = 89% |
| 68% | 20% | (80 − 54.4) ÷ 0.2 = 128% – not possible; for 70%: 78% |
A heavily weighted final is a real chance to recover from a weak start, while a light one mostly protects a good grade you have already earned.
When "current grade" is not simple
- Weighted categories: if homework, quizzes and midterms have different weights, your current grade is their weighted average using only the categories completed so far. The average calculator explains weighted averages with an example.
- Points-based courses: if the course is out of, say, 1,000 points and the final is 250 of them, the final weight is 25% and your current grade is points earned ÷ 750.
- Dropped lowest scores or replacement policies (where the final replaces a midterm) change the arithmetic; follow your syllabus.
From course grades to GPA
Once you know your likely letter grade, the GPA calculator shows how it affects your term and cumulative GPA, weighted by credits. A B instead of a C in a four-credit course lifts a 15-credit term GPA by about 0.27.
Common mistakes
- Using a weight as a whole number in the formula. 25% must be 0.25, otherwise the answer is 100 times too small.
- Including the final in the current grade. "Current" means everything except the final.
- Assuming rounding. Some teachers round 79.5% up to 80%, others do not. Aim slightly above the cut-off.
This calculator only does the arithmetic. Your official grade is set by your instructor and institution, including any curve, rounding or extra credit.
Frequently asked questions
What do I need on my final to get a B?
Use (80 − current × (1 − w)) ÷ w. With 82% now and a final worth 25%, you need (80 − 61.5) ÷ 0.25 = 74%.
How do I calculate my grade with the final exam?
Multiply your current grade by (1 − final weight), multiply your final score by the weight, and add. 82% now, 74% on a 25% final: 82 × 0.75 + 74 × 0.25 = 80%.
What if I need more than 100% on the final?
Then the target cannot be reached through the final alone. Check whether extra credit, dropped scores or a curve apply, or set a lower target.
How much can a final exam change my grade?
Between a zero and a perfect score the final moves your grade by exactly its weight. A 25% final can change the course grade by up to 25 percentage points.
Sources
- University course syllabi commonly define final grades as weighted averages of assessment categories; check your own syllabus for weights and cut-offs.
- College Board, How to convert your GPA to a 4.0 scale (letter grade and percentage bands).
Last reviewed 8 October 2026. Results are estimates; see our disclaimer.