It’s the most-Googled question of every semester: “What do I need on the final to get the grade I want?” The math isn’t hard, but doing it in your head — with weighted categories — at 11pm before an exam is exactly when mistakes happen. Here’s the formula, and a faster way to never do it by hand again.
First, how a weighted grade works
Most courses weight each assessment: homework 20%, quizzes 15%, midterm 25%, final 40%. Your overall grade is each score multiplied by its weight, added up, divided by the total weight:
overall = Σ(score × weight) ÷ Σ(weight)
So an 88 on homework worth 20% contributes 88 × 20 = 1760 “weighted points” toward a 100-point total.
The “what do I need on the final?” formula
Say you want to finish at 90%, the final is worth 40%, and everything else is done. Add up the weighted points you’ve already earned, then solve for the score you need on the final:
needed = (target × total‑weight − earned‑points) ÷ final‑weight
Worked example. You’ve earned 92 on homework (20%), 85 on quizzes (15%) and 88 on the midterm (25%) — that’s 92×20 + 85×15 + 88×25 = 1840 + 1275 + 2200 = 5315 points out of a possible 6000 so far. To hit 90 overall (90 × 100 = 9000 total points needed), the final (40%) must supply 9000 − 5315 = 3685 points, so 3685 ÷ 40 = 92. You need a 92 on the final.
Two things fall out for free: if the number comes out above 100, the grade is out of reach and you can plan accordingly; if it comes out at or below 0, you’ve already locked it in.
Or just type it in
Studio Convert’s Grades workspace does the weighting for you — enter each assessment’s weight and the scores you have, and it shows your current standing, each letter grade, and a “what do I need on the final?” solver: set your goal, pick the assessment you haven’t taken yet, and it tells you the exact score you need (or that it’s already secured, or out of reach). There is no formula to remember and no late-night arithmetic.
Studio Convert is coming to macOS — a native menu-bar app, $39.99/year with a 14-day free trial. No account, nothing leaves your Mac.
