The formula
Needed = (goal − current × (1 − w)) ÷ wHere w is the final's weight as a decimal, so 20% is 0.2. Your current grade covers the rest of the course, 1 − w, and the final makes up the remainder.
Worked example
You have 84% going into a final worth 20%, and you want to finish with at least 80%.
- The part of the course already done is worth 84 × 0.8 = 67.2 points.
- You need 80 − 67.2 = 12.8 more points from the final.
- The final is worth 20 points of the 100, so you need 12.8 ÷ 0.2 = 64% on it.
A perfect final would take you to 67.2 + 20 = 87.2%, so an A is out of reach this term, but a B+ (87%) is still possible.
Before you rely on it
- Use your grade exactly as your gradebook shows it, before any rounding.
- If more work is still to be graded besides the final, your current grade will change, so the score you need will too.
- Some teachers replace your lowest test with the final, or let the final replace a grade. Then this formula doesn't apply. Check your syllabus.
Common questions
- How do I figure out what I need on my final?
- Subtract your current grade times the share of the course that's already done from the grade you want, then divide by the final's weight. With 84% now and a final worth 20%: (80 - 84 x 0.8) / 0.2 = 64%. You need 64% on the final to finish with an 80%.
- What if I need more than 100%?
- Then that grade is out of reach on the final alone, unless there's extra credit or other work still to be graded. The calculator also shows the best grade you can reach with a perfect final.
- What if my final is worth points instead of a percentage?
- Divide the final's points by the total points in the course to get its weight. A 200-point final in a 1,000-point course is worth 20%.
- What happens if I skip the final?
- A zero counts in full. With 84% now and a final worth 20%, a zero would leave you at 67.2%.