To find the final-exam score you need, use needed = (target − current × (1 − weight)) ÷ weight, where the weight is the final's share of your grade as a decimal. With an 88% current grade, a final worth 25% (0.25), aiming for a 90%, you need (90 − 88 × 0.75) ÷ 0.25 = 96%. If the answer comes out above 100%, the target is impossible.
Key takeaways
- needed = (target − current × (1 − weight)) ÷ weight.
- Weight is the final's percent of your grade, as a decimal (25% → 0.25).
- An answer over 100% means the target is out of reach.
- To hold your grade, you need to score your current grade on the final.
- Estimates only — confirm how your final is weighted in the syllabus.
The formula, explained
Your final course grade is a weighted average of two things: everything before the final (which counts for 1 − weight) and the final itself (which counts for weight). Set that equal to your target and solve for the final score:
Everything is a percentage; the weight is a decimal between 0 and 1. The final grade calculator runs this for you and flags targets that need more than 100%.
Worked example: 88% going in, 25% final, want a 90%
You have an 88% with a final worth 25% of the grade, and you want to finish with a 90%. First, your work so far counts for 1 − 0.25 = 0.75, contributing 88 × 0.75 = 66 points. You need a 90 total, so the final must supply 90 − 66 = 24 points, and it is worth 0.25 of the grade: 24 ÷ 0.25 = 96%. A tough but reachable score.
How the weight changes the answer
| Final weight | Score needed for a 90% |
|---|---|
| 10% | 108% — impossible |
| 20% | 98% |
| 25% | 96% |
| 40% | 93% |
| 50% | 92% |
Based on an 88% current grade and a 90% target. A heavier final makes a target easier to reach, because the final can pull your average further.
When a target is impossible
If the required score is above 100%, no final can get you there — the math has run out of room. That is your cue to set a realistic target (the same calculator shows what you'd land on with, say, a 100% final). Once you know your current grade, the weighted grade calculator and semester grade calculator help you confirm exactly where you stand before the final.
Frequently asked questions
How do I calculate what I need on the final exam?
Use needed = (target − current × (1 − weight)) ÷ weight, with the weight as a decimal. An 85% going in, a 20% final, and a 90% target needs (90 − 85 × 0.80) ÷ 0.20 = 110% — impossible.
What if the score I need is over 100%?
A required score above 100% means the target is out of reach: even a perfect final cannot get you there. The final grade calculator flags impossible targets automatically.
What grade do I need to keep my current average?
To hold steady, score your current grade on the final: a 90% average needs a 90% final to stay at 90%, whatever the final’s weight.
Sources: the needed-score formula is derived from the weighted-average definition of a course grade (current × (1 − weight) + final × weight). Letter-grade bands use the common US scale; schools set their own cutoffs and decide how the final exam is weighted, so confirm yours in the syllabus.
Last reviewed 2026-06-28