This calculator answers one narrow, useful question: given what you have scored so far and how much the final is worth, what do you need on it? The formula is straightforward, and the answer is frequently reassuring — or, occasionally, clarifying in a way that is better learned before the exam than after.
Required final score = (target − current × (1 − weight)) ÷ weight, where weight is the final's share of the grade expressed as a decimal.
A worked example
You have 82% going in, the final is worth 30%, and you want an overall 90%. Your existing work contributes 82 × 0.70 = 57.4 points. You need 90 − 57.4 = 32.6 points from the final, and since it is worth 30 points, you need 32.6 ÷ 0.30 = 108.7%. That is not achievable without extra credit, and knowing it a week early lets you aim at a realistic target instead.
What you need for a 90%, starting from various positions
| Current grade | Final worth 20% | Final worth 30% | Final worth 40% |
|---|---|---|---|
| 95% | 70% | 78% | 82.5% |
| 88% | 98% | 94.7% | 93% |
| 85% | 110% | 101.7% | 97.5% |
| 80% | 130% | 113.3% | 105% |
How to read a number above 100
- It is not achievable through the exam alone — reset the target to the next attainable grade and work to that.
- Ask about extra credit before the final, not after, when it is still possible for an instructor to offer it.
- Check whether the final replaces a lower midterm score; some courses allow this and it changes the arithmetic entirely.
- Confirm the weights on the syllabus. Estimating from memory is the most common source of a wrong answer here.
The upside case
The calculation cuts both ways, and just as often shows that a modest score protects the grade you already have. If you are at 93% with a final worth 20%, you can score 78% and still finish with an A. Knowing your floor is as valuable as knowing your ceiling — it tells you which exam genuinely deserves the extra night of study and which one does not.