You already have most of your grades. Here is the one-line formula that tells you exactly what you need on the final — no guessing.
Two weeks out from finals, every student asks the same question: *what do I actually need to score to keep my grade?* The answer is not a guess — it is a two-variable formula that takes 30 seconds with a calculator.
Required final = (Target − Current × (1 − Weight)) ÷ Weight
Where:
You have an 87% average. The final is worth 30% of your course grade. You want to finish with 90%.
Required final = (90 − 87 × 0.70) ÷ 0.30 = (90 − 60.9) ÷ 0.30 = 97%.
That is the honest answer — a 97 on the final locks in a 90 course grade. If a 97 is unrealistic, you can work backwards: what does an 85 on the final leave you with? 87 × 0.70 + 85 × 0.30 = 60.9 + 25.5 = 86.4%.
Two mistakes account for 90% of wrong answers here:
To find the lowest final grade that still passes (say, 60%):
Required = (60 − Current × (1 − Weight)) ÷ Weight
If your current average is 72% and the final is 25% weighted: Required = (60 − 72 × 0.75) ÷ 0.25 = (60 − 54) ÷ 0.25 = 24%. You would need to actively try to fail.
Plug the low end of your target letter as "Target" to see the minimum final score for that grade.
Once you know the required score, ask two questions:
1. How far is it from your current average? Anything within 10 points is realistic with normal prep. 15+ points above your average means you should target a lower course grade or negotiate extra credit early. 2. Which topics carry the most weight on the final? Past finals and the syllabus outline are your best guides — 70% of study time on the 30% of topics most likely to appear.
Does this formula work if the final replaces the lowest exam? No — that policy changes your current average dynamically. Recalculate your "current" assuming the final replaces the lowest score, then apply the formula.
What if extra credit is available? Add expected extra-credit points to your current average before running the formula. Be conservative — extra credit usually caps at a few percent.
Can I use this for GPA instead of percentage? The math is identical if all classes are equal credit; use credit-hour weighting for a full GPA projection — see our GPA guide.
Why is my required grade above 100? It literally cannot be reached — the target grade is not achievable given your current average and the final's weight. Recalculate with a lower target.
Should I round the required score up? Yes. If the formula says 88.4, plan for 90+ — professors round in both directions and one bad question shouldn't sink you.
Run your own numbers instantly with our free Percentage Calculator — it handles the weighted-average math and lets you save scenarios for every class.