The Formula
The grade you need on your final exam is determined by one equation:
gradeNeeded = (desiredGrade − currentGrade × currentWeight/100) / (finalWeight/100)Where:
desiredGrade= the overall course grade you want (0–100)currentGrade= your grade from all work done before the final (0–100)currentWeight= percentage of the course grade that comes from work already done (e.g., 70 if the final is worth 30%)finalWeight= 100 − currentWeight
This formula is derived from the weighted average definition: your final course grade is the weighted sum of your pre-final grade and your final exam grade.
If your final course grade must equal D:
D = C × (cw/100) + G × (fw/100)Solving for G (grade needed on final):
G = (D − C × cw/100) / (fw/100)Worked Example: Not Achievable
Consider a student with:
- Current grade: 82%
- Current work weight: 70% of the course
- Desired grade: 90%
Final weight = 100 − 70 = 30%
Grade needed = (90 − 82 × 0.70) / 0.30
= (90 − 57.4) / 0.30
= 32.6 / 0.30
= 108.7%
The student would need to score 108.7% on the final — which is mathematically impossible (assuming no extra credit). This target is not achievable. The student should consider adjusting their target grade or discussing extra credit options with the professor.
Worked Example: Achievable
The same student, but targeting 85% instead of 90%:
Grade needed = (85 − 82 × 0.70) / 0.30
= (85 − 57.4) / 0.30
= 27.6 / 0.30
= 92%
A score of 92% on the final is achievable, though it requires strong exam performance.
Feasibility Categories
| Grade needed | Classification |
|---|---|
| Below 95% | Achievable — within reach with solid preparation |
| 95%–100% | Requires perfect exam — theoretically possible but no margin for error |
| Above 100% | Not achievable — mathematically impossible without extra credit |
The 95% threshold for “requires perfect exam” is a practical guideline: a score that high leaves almost no room for error in any individual question.
What to Do When You Can’t Hit Your Target
If the calculator tells you the grade you need is over 100%, you have several options:
Adjust your target grade. Enter lower values for desiredGrade until you find a target that requires a grade below 100% on the final. This tells you the highest overall grade you can still realistically achieve.
Investigate extra credit. Some professors offer extra credit assignments that can add percentage points to your final grade or to the overall course average. Ask specifically — professors’ policies vary widely.
Understand the consequence. If passing the course requires a specific grade (e.g., a B to maintain a scholarship), and that grade is no longer achievable, it may be necessary to discuss the situation with an advisor about course withdrawal, grade replacement policies, or academic appeals.
Check your course policy. Some courses have grade replacement policies or allow dropping the lowest exam score. Your final exam might not actually be worth what you assumed — check the syllabus again.
Common Mistakes
Confusing course weight with final exam weight. “Current weight” is the percentage of the total course grade that comes from work already graded — homework, quizzes, midterms, etc. If you enter 30 (meaning the final is worth 70%), when the final is actually worth 30%, your result will be wrong. Re-read your syllabus carefully.
Including the final in “current grade.” Your current grade should reflect only work completed before the final. If you received a practice final grade or if a professor posts a preliminary grade that already includes an estimate for the final, do not use that number.
Assuming “current grade” is the same as “weighted grade.” In courses where each assignment type has its own weight, your overall course average might differ from a simple arithmetic mean of your scores. Check your learning management system (Canvas, Blackboard, Moodle) for a calculated running grade rather than calculating it manually.
Practical Study Strategy
The calculator does not just tell you whether your goal is achievable — it tells you how far you are from it, which lets you make informed study decisions.
If you need 75% on the final to hit your target, your risk is lower; you can allocate study time across multiple subjects. If you need 95%, you need to prioritise this course. If you need 108%, you need to recalibrate your goal before the final so you can set realistic expectations.
Knowing the number helps you direct effort where it matters.