Curve Grade Calculator
See your curved grade three common ways — top-score bump, proportional scaling and the square-root curve.
How it works
top-score: raw + (100 − high) · proportional: raw ÷ high × 100 · square-root: √raw × 10
Curving rescales scores when a test runs hard. The top-score (flat) method adds the same points to everyone so the class’s best paper becomes 100%. Proportional scaling stretches each score by the same factor, and the square-root curve √raw × 10 lifts low scores the most while barely moving high ones. Instructors pick one deliberately — a flat bump preserves gaps between students, while the square-root curve compresses them.
Worked example
Your raw score is 78% and the class high is 88%. Top-score bump: 78 + (100 − 88) = 90%. Proportional: 78 ÷ 88 × 100 = 88.6%. Square-root: √78 × 10 = 88.3%.
Frequently asked questions
Which curve is the "real" one?
There isn’t a universal rule — curving is at the instructor’s discretion. The flat top-score bump and the square-root curve are the two most common; ask which your class uses before assuming a number.
Does a curve ever lower a grade?
A pure top-score or square-root curve never lowers a score. Some statistical curves that fit grades to a target distribution can pull high scores down, but the three methods here only raise or hold your grade.
Why does the square-root curve help weaker scores most?
Because √x grows fastest for small x. A 36 becomes 60 (a 24-point jump) while an 81 becomes 90 (only 9 points), so the gap between the bottom and top of the class narrows.
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This calculator is for educational purposes. Double-check important results before acting on them.