Results are estimates
This works when the final exam counts for a fixed share of your course grade and your current grade covers everything else. Schools and teachers weight grades in different ways, round differently, or drop scores, so check your course syllabus or ask your teacher.
The formula
Your course grade is a weighted average: course grade = current grade × (1 − w) + final exam score × w, where w is the final’s share of the grade (for example 0.20 for 20%).
Solving for the final exam score: needed score = (target grade − current grade × (1 − w)) ÷ w.
If the result is above 100%, the target cannot be reached without extra credit. If it is 0% or less, you reach the target whatever you score on the final.
Worked examples
A reachable target
Current grade 85%, final worth 25%, target 80%: (80 − 85 × 0.75) ÷ 0.25 = (80 − 63.75) ÷ 0.25 = 65%. You need at least 65% on the final.
A target out of reach
Current grade 85%, final worth 20%, target 90%: (90 − 85 × 0.8) ÷ 0.2 = (90 − 68) ÷ 0.2 = 110%. Even a perfect final gives 85 × 0.8 + 100 × 0.2 = 88%.