It’s the last week before exams, the syllabus says the final is worth 30%, and you’re sitting on an 85. The question is simple: what do I need on my final to get the grade I want? The maths is simple too, once you know the formula, and knowing the answer changes how you spend your revision time.
This guide explains the formula, walks through examples, shows how to find the numbers you need, and covers what to do when the answer is “more than 100%”. For instant results, our free calculator does it for you.
The formula
Your final course grade is a weighted mix of two things: everything you’ve done so far, and the exam.
course grade = current grade × (1 − final weight) + exam score × final weight
Solve for the exam score and you get the number you need:
needed = (target − current × (1 − weight)) ÷ weight
Weights are decimals: a 30% final is 0.3. With current = 85, weight = 0.3 and target = 88: needed = (88 − 85 × 0.7) ÷ 0.3 = (88 − 59.5) ÷ 0.3 = 95.
Step 1: find your current grade
You need your grade on everything marked so far, as a percentage out of 100, excluding the final. Most online gradebooks show this as “current score”. If yours shows a running total that counts the unwritten final as zero, don’t use that; it’ll make the calculation far too pessimistic. If you have category averages and weights instead, combine them with our Grade Calculator.
Step 2: find the final’s weight
Check the syllabus. It’s usually stated as a percentage. If the course uses points, divide the final’s points by the course total: a 200-point final in an 800-point course is 200 ÷ 800 = 25%. If the final replaces a midterm or has a “whichever is higher” rule, the effective weight is different, so ask your teacher.
Step 3: pick a target and calculate
Here’s a full example at 85% current and a 30% final:
| Target | Letter (plus/minus) | Needed on the final |
|---|---|---|
| 93% | A | 111.7% — not possible |
| 90% | A− | 101.7% — not possible |
| 87% | B+ | 91.7% |
| 83% | B | 78.3% |
| 80% | B− | 68.3% |
| 70% | C− | 35% |
The table tells a clear story: an A is off the table, a B+ needs a very strong exam, and a B is safe with a solid performance. That’s the information you want before deciding how many hours to put in.
What do I need on my final if the weight is bigger?
The heavier the exam, the wider the range of outcomes. At 85% current:
- 20% final: course grade can only move between 68% and 88%. Getting 90% overall is impossible; holding a B needs 75% on the exam.
- 40% final: the range is 51% to 91%. An A− (90%) needs 97.5%; a B needs 80%.
- 50% final: the range is 42.5% to 92.5%. An A− needs 95%; a B needs 81%.
A heavy final is a bigger risk but also a bigger opportunity. Each 10% you gain on the exam adds weight ÷ 10 points to your grade, so 3 points for a 30% final and 5 points for a 50% one.
When the answer is more than 100%
If the required score is above 100%, the target is unreachable through the exam alone. Your options are to aim for the next letter down, or to ask about extra credit, a dropped assignment, a regrade of earlier work, or whether the course curves. Many students revise frantically for a grade the numbers already rule out; checking first avoids that.
If the required score is zero or negative, the opposite is true: you’ve already secured the target, and your effort is better spent on a course where the final still matters.
Using the answer to plan revision
- Work out the needed score for the letter you want and the letter below it. The gap between them is your safety margin.
- Look at past exam scores. If you’ve never scored above 85% on this teacher’s tests, a target that needs 95% is a stretch.
- If two courses need attention, prioritise the one where the exam can change the letter grade.
- Recalculate after any late assignment or regrade comes back.
Common mistakes
- Using a “total so far” that already counts the final as zero.
- Entering the weight as 30 in a formula that expects 0.3.
- Forgetting that the final may be split into parts, such as a written paper and a practical, with separate weights.
- Assuming the letter cut-offs from another school; the syllabus decides.
Summary
To find what you need on your final, take your current grade excluding the exam, the exam’s weight as a decimal, and your target, then calculate (target − current × (1 − weight)) ÷ weight. Check whether the result is possible, look at the letter below as a fallback, and plan your revision around the answer. The final grade calculator gives you the full table in one go, and the GPA Calculator shows what the result means for your GPA. For background on how grading works in different systems, see this overview of grading in education.
