Short answer: score needed = (target − current grade × (1 − w)) ÷ w, where current grade is your percentage on the work marked so far and w is the final exam’s weight as a decimal.
The Idea Behind the Formula
Your final grade has two parts: the work already marked, which counts for (1 − w) of the course, and the final exam, which counts for w.
Exam score needed = (target − current grade × (1 − w)) ÷ w
Use percentages for the grades and a decimal for the weight, so a 40% exam means w = 0.40. Not sure of your current grade? Work it out first with our guide to calculating your current grade.
Step-by-Step Example
Your current grade is 68%, the final is worth 40%, and the pass mark is 50%.
- Work out the weight of completed work: 1 − 0.40 = 0.60.
- Multiply: 68 × 0.60 = 40.8 points already earned.
- Subtract from the target: 50 − 40.8 = 9.2.
- Divide by the exam weight: 9.2 ÷ 0.40 = 23%.
If the exam is marked out of 80, that is 0.23 × 80 = 18.4 marks. The same current grade gives very different requirements for different targets:
| Target final grade | Working | Exam score needed |
|---|---|---|
| 50% | (50 − 40.8) ÷ 0.40 | 23% |
| 60% | (60 − 40.8) ÷ 0.40 | 48% |
| 70% | (70 − 40.8) ÷ 0.40 | 73% |
| 80% | (80 − 40.8) ÷ 0.40 | 98% |
Converting the Percentage Into Marks
Exams are usually marked in whole numbers, so round the marks up. Suppose the final is out of 60 and you need 48%. That is 0.48 × 60 = 28.8 marks. Test both neighbours. With 28 marks you score 46.67%, and your final grade is 40.8 + 0.40 × 46.67 = 59.47%, which misses a 60% target. With 29 marks you score 48.33%, giving 40.8 + 0.40 × 48.33 = 60.13%, which meets it. The answer is 29 marks, not 28.
How to Read the Answer
- Below 0%. You have already secured the target. For example, with a current grade of 85%, a 20% final and a 50% target, the formula gives (50 − 85 × 0.80) ÷ 0.20 = −90%. Check for a minimum exam mark before relaxing.
- Between 0% and 100%. The target is reachable. Compare the figure with what you usually score on exams like this one.
- Above 100%. The target is not possible. Choose a lower one.
When the Target Is Out of Reach
Suppose your current grade is 40%, the final is worth 30% and you want 70%. The formula gives (70 − 40 × 0.70) ÷ 0.30 = 42 ÷ 0.30 = 140%. Any answer above 100% means the target is impossible. Lower it: for a 50% target, (50 − 28) ÷ 0.30 = 73.33%, which is demanding but possible.
When Other Work Is Still to Come
If more than the final remains, use weighted points earned over the whole course instead. Needed score = (target − weighted points earned) ÷ weight of the final. With 52.0 weighted points earned, a 30% final and a 60% target, you need (60 − 52.0) ÷ 0.30 = 26.67%. Any other unmarked work needs to be counted in your assumptions, or the answer will be wrong.
What If the Final Is Split Into Two Papers?
If the exam has two equally weighted papers, work out the overall exam score you need first, then split it. Suppose you need 73% overall and score 70% in Paper 1. Paper 2 must make up the difference: 2 × 73 − 70 = 76%, because (70 + 76) ÷ 2 = 73. If the papers carry different totals, add the marks and totals together instead of averaging percentages.
Turning a Letter Grade Into a Target
The formula needs a target percentage. If your goal is a letter grade, find the lowest percentage that earns it in your institution’s grading table and use that as the target. For example, if a B starts at 60%, set the target to 60. Grade bands differ between institutions and sometimes between courses, so use the table that applies to you. Aim slightly above the boundary, because a result just under it may not be rounded up.
Turning the Number Into a Revision Plan
A required score tells you how much of the paper you need to get right, which helps you choose where to spend revision time. Say the exam is out of 100 in three sections: A (20 marks), B (40 marks) and C (40 marks), and you need 73. A target breakdown might be 16 out of 20 in A, 28 out of 40 in B and 29 out of 40 in C, which adds up to 73. This is a plan, not a prediction. It shows which sections need the most careful preparation.
Once you have the number, put the exam date into the Exam Countdown to see how many days remain, and use the Study Schedule Generator to spread revision across them. Planning backwards from the score you need is more useful than revising everything equally and hoping.
Common Mistakes to Avoid
- Mixing percent and decimal weights. Use 0.40, not 40, in the formula.
- Using the wrong current grade. It should be your grade on completed work, not the total with the final counted as zero.
- Forgetting a minimum exam mark. Some courses require a pass on the exam itself as well as overall.
- Assuming the pass mark. It may be 40%, 50% or higher, so check your handbook.
- Aiming for the exact minimum. Leave a margin, because exams rarely go exactly to plan.
Checking the Target Against Reality
Before you commit to a target, compare the required score with real evidence. Look at your marks on past papers, practice questions and earlier tests in the course, and be honest about whether the required figure sits above or below them. If it is well above, decide whether the target is realistic or whether you need a much stronger revision plan. If it is comfortably below, resist the urge to coast. Recalculate once your timetable or the exam weighting is confirmed, because a change in either alters the answer. A result you can plan around is worth more than one you only hope for.
Check Your Work With BioScribe
BioScribe’s Grade Calculator calculates weighted grades and works out the score you need on a final exam. Use it to check each row of the table above and to try different target grades.
Frequently Asked Questions
Can I pass if I fail the final exam?
Sometimes. If the pass mark applies only to your overall grade, a low exam score can still be enough, as the 23% example shows. Many courses also set a minimum exam mark, so check the rules.
How do I use a weight given as a percentage?
Convert it to a decimal by dividing by 100. A 40% exam becomes 0.40 in the formula.
Should I plan for the exact score the formula gives?
No. Treat it as the minimum and aim higher, because there is always some uncertainty in how an exam will go.
What if my course uses a curve or bonus marks?
The formula uses your real marks. If your instructor adjusts scores, ask how and apply the formula to the adjusted figures.
Can I use this formula for a resit?
Only if the resit is graded the same way. Many institutions cap resit results or replace the original assessment, so check the resit rules before calculating.
Where do I find the weight of my final exam?
Look in the syllabus, course outline or assessment handbook. If it is not stated, ask your instructor, because guessing the weight makes the answer unreliable.
Conclusion
Put your current grade, the exam weight and your target into one formula, and a vague worry becomes a number you can plan around. If that number is far above what you usually score, revise your target early rather than after the exam.
