Exam Curve Calculator
When a test turns out harder than planned, instructors often curve the grades, but there is no single curve: the three most common are a flat point add, a scale-to-top, and a square-root curve, and each treats your score differently. This calculator applies all three to your raw percentage at once so you can see exactly what an announced curve does to your grade. Enter your raw score, the flat points to add, and the class top score, and compare the curved results.
Exam curve formulas
Flat add = min(100, raw + points to add)
Scale to top = min(100, raw / class top * 100)
Square-root curve = min(100, 10 * sqrt(raw))
Most generous = the highest of the three
Each method is capped at 100 because no curve normally produces a score above full marks. The square-root curve uses the raw percentage as the value under the root, the standard form for a 0 to 100 scale.
Worked example
Raw score 72, add 5 points, class top 88. Flat add = 72 plus 5 = 77.00. Scale to top = 72 / 88 times 100 = 81.82. Square-root curve = 10 times the square root of 72 = 84.85. The most generous of the three here is the square-root curve at 84.85.
Exam curve: frequently asked questions
What is a curved exam grade?
Curving adjusts raw scores upward (occasionally downward) using a fixed rule, usually because the test was harder or easier than intended. Common rules are: add a flat number of points to everyone, scale so the highest raw score becomes 100, or apply a square-root curve. This calculator shows all three so you can see how each treats your score.
How does a square-root curve work?
A square-root curve replaces each percentage with 10 times the square root of that percentage. A raw 49 becomes 10 times the square root of 49 = 70. It lifts low scores more than high ones and never pushes a score above 100, which is why instructors favour it for difficult tests.
How does a scale-to-top curve work?
Scale-to-top divides every raw score by the highest score in the class and multiplies by 100, so the top student gets 100 and everyone else rises in proportion. Enter the highest raw percentage achieved to use this method.
Which curve will my instructor use?
Only your instructor knows: curving is at their discretion and many do not curve at all. This calculator shows what each common method would produce so you can interpret an announced curve, not predict whether one will happen.
Sources and method
- Method: three standard grading-curve rules (flat point add, proportional scale-to-top, and the square-root curve, 10 times the square root of the percentage). All inputs are user-supplied.
- U.S. Department of Education general resources: ed.gov.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.