How weighted grades work
A weighted average multiplies each component by its weight, adds the results, and divides by the total weight:
Average = Σ (score × weight) ÷ Σ weight
Weights do not have to sum to 100 — the formula normalises them — but they usually do, and it is worth checking that yours do because a mismatch is usually a transcription error rather than an intentional scaling.
Worked example
Three components: quizzes at 30% scoring 78, a midterm at 45% scoring 85, a final at 25% scoring 92.
Weighted = (78 × 30 + 85 × 45 + 92 × 25) ÷ 100 = (2,340 + 3,825 + 2,300) ÷ 100 = 84.65%.
A plain average would be (78 + 85 + 92) ÷ 3 = 85.0%. The difference is small here because the scores are close, but it grows with spread: with quizzes at 50 and a final at 100, the weighted result is 78 while the plain average is 75. Weighting pulls the result toward the heavily weighted component, which is the whole intent.
The formula for the final exam score you need
Setting the weighted average equal to a target T and solving for the missing score x:
x = (T × Σw − Σ(wᵢsᵢ for completed components)) ÷ w_final
Worked example: 30% quizzes at 78 and 45% midterm at 85, target 90%, final worth 25%.
Σ(weighted, completed) = 78 × 0.30 + 85 × 0.45 = 23.4 + 38.25 = 61.65. Target contribution = 90 × 1.00 = 90. So x = (90 − 61.65) ÷ 0.25 = 113.4.
That is above 100, which means 90% is not reachable in this course even with a perfect final. The highest achievable is (61.65 + 100 × 0.25) = 86.65%. Knowing that before the exam is worth more than the calculation itself, and the final grade calculator is built to surface exactly this case.
Weights, curves and what they change
Three different mechanisms are often called "curving", and they are not interchangeable:
- A curved raw-to-letter mapping — the scores are unchanged; only the conversion to grades applies the curve. A 78 might be a B in a curved class and a C- in an uncurved one.
- Adding a bonus to every score — shifts everything, so rankings stay the same and the course average rises.
- Removing the lowest exam — changes the weighting, so the course average can fall even though nothing else changed.
Because the mechanism decides the outcome, any projection should be checked against the course's published policy rather than a generic percentage table. The GPA and weighted grades guide works through these cases in detail.
How the percentage becomes a GPA
The mapping is a convention of your institution. A common 4.0 scale:
93–100 → 4.0 · 90–92 → 3.7 · 87–89 → 3.3 · 83–86 → 3.0 · 80–82 → 2.7 · 77–79 → 2.3 · 73–76 → 2.0 · 70–72 → 1.7 · 67–69 → 1.3 · 60–66 → 1.0 · below 60 → 0
Other institutions use different cut-offs, add ±0.3 marks at the top, or require a 4.0 for an A rather than 93. The number this calculator shows is the common convention, useful as a check and unreliable as an authority. The grade scale converter lets you compare scales directly.
Frequently asked questions
How do I calculate a weighted grade?
Multiply each component score by its weight, add them, and divide by the total weight. The calculator also converts the result to GPA points and a letter grade using a common 4.0 scale.
Do the weights have to add up to 100?
No — the formula normalises them, so any relative weights work. But if yours do not total 100 it is usually a mistake rather than an intentional scaling, and the calculator flags it.
What score do I need on the final exam?
Set the weighted average to your target and solve for the missing score. If the result is above 100, the target is not achievable — the calculator shows that case explicitly rather than returning an impossible number.
Does a curve change my course average?
It depends on the mechanism. A curved raw-to-letter mapping does not change the weighted average at all — only the grade. A bonus adds to scores, and dropping an exam changes the weights. Check the course policy before projecting.