The formula
To find the score you need on the final, use this formula, with the weight of the final written as a decimal (20% is 0.20).
Needed score = (target − current × (1 − w)) ÷ w.
- target: the course grade you want, in percent
- current: your grade before the final, in percent
- w: the weight of the final as a decimal
Worked example: reaching an 80
Your current grade is 84%, the final is worth 20%, and you want an 80%. Here w = 0.20, so (1 − w) = 0.80.
Needed score = (80 − 84 × 0.80) ÷ 0.20 = (80 − 67.2) ÷ 0.20 = 12.8 ÷ 0.20 = 64. You would need a 64% on the final.
Worked example: reaching a 90
With the same current grade and weight, a target of 90 gives (90 − 67.2) ÷ 0.20 = 22.8 ÷ 0.20 = 114. A score of 114% is not possible without extra credit, so a 90 is out of reach unless the course offers extra points. The final grade calculator on this site will show a result above 100 so you can see this.
What counts as your current grade
The current grade must be the grade before the final, measured on the same scale the course uses for the final grade. If the course is weighted by category, use the weighted grade so far, not a simple average of scores. Do not include a grade that already contains the final.
Check the syllabus for special rules. Some teachers let the final replace a lower test score, or drop the lowest grade, and the formula above does not model those rules. Others require a minimum score on the final to pass. If any of these apply, adjust the current grade first or ask your teacher.
Have a correction or a suggestion? Tell the studio.