The Final Grade Formula

Where the formula comes from

A course grade is a weighted average of its parts. If the final is worth W of the course, everything else is worth (1 − W). Score S on the final and your course grade is:

You want the course grade to equal your target T. Set them equal and solve for S: T = current × (1 − W) + S × W, so S × W = T − current × (1 − W), and dividing by W gives the formula above. That is all there is — one weighted average, rearranged. The term current × (1 − W) is the points you have already banked; the formula asks how much of the target is still missing and spreads it over the final's weight.

Four worked examples

Current 85%, final worth 30%, target 90% — Above 100 — out of reach

Banked points: 85 × 0.7 = 59.5. Still needed: 90 − 59.5 = 30.5 points from the final. Score required: 30.5 ÷ 0.3 = 101.67%. That is above 100%, so the target cannot be reached — even a perfect final tops out at a course grade of 89.5%.

Current 82%, final worth 25%, target 85% — A comfortable, reachable target

Banked points: 82 × 0.75 = 61.5. Still needed: 85 − 61.5 = 23.5 points from the final. Score required: 23.5 ÷ 0.25 = 94%. A real score: reach it and you finish at exactly 85%; every point above it adds 0.25 points to your course grade.

Current 95%, final worth 20%, target 90% — Coasting room — a modest score holds the grade

Banked points: 95 × 0.8 = 76. Still needed: 90 − 76 = 14 points from the final. Score required: 14 ÷ 0.2 = 70%. A real score: reach it and you finish at exactly 90%; every point above it adds 0.2 points to your course grade.

Current 95%, final worth 5%, target 90% — Negative — already locked in

Banked points: 95 × 0.95 = 90.25. Still needed: 90 − 90.25 = -0.25 points from the final. Score required: -0.25 ÷ 0.05 = -5%. A negative requirement means the target is already secured: your banked points alone exceed it, so any score — including zero — keeps you at or above 90%.

Edge cases and honest limits

• Weight of zero. If the final is worth nothing, the formula divides by zero — correctly: a weightless exam cannot move your grade at all.
• Unfinished coursework. The formula assumes everything except the final is settled. If other work is outstanding, its weight belongs in the calculation too — the weighted grade calculator untangles multi-category courses.
• Curves and replacements. A curved final, or a final that replaces your lowest test, breaks the simple weighted-average model. Treat the formula's answer as the un-curved baseline.
• Rounding. Schools differ on whether 89.5 rounds up. If your needed score lands within a point of a boundary, ask your teacher rather than trusting any calculator.

Prefer not to do algebra during exam week? The final grade calculator runs this exact formula on your numbers and lays out every letter grade at once.

Frequently asked questions