CalcRipple

Grade Curve Calculator

This grade curve calculator adjusts a raw percentage using a method you choose. For the square-root curve, curved percentage = 10 × square root of raw percentage: 64% becomes 80.00%. Adding points and scaling to a highest score produce different results. Your instructor decides which, if any, applies.

Created by Dennis Norton · Updated November 1, 2026

How to use the grade curve calculator

  1. Enter your raw percentage, not your raw points.
  2. Select square root, add percentage points, or highest-score scaling.
  3. For addition, enter the bonus and decide whether to cap the result at 100%. For scaling, enter the highest class percentage.
  4. Read the adjusted score and the increase in percentage points.

If your test was not scored out of 100, first divide your points earned by the possible points and multiply by 100. Enter the highest score on that same percentage scale.

Three grade curve formulas

Square-root curve

Curved percentage = 100 × √(raw percentage ÷ 100) = 10 × √(raw percentage).

The nonnegative root is used. Zero stays zero and 100 stays 100. This method does not use the class average or class rank.

Add percentage points

Curved percentage = raw percentage + bonus points.

The bonus is an addition in percentage points, not a percentage increase. If you choose the cap, values above 100 are reduced to 100, and the result explicitly reports the uncapped value too.

Scale the highest score to 100%

Curved percentage = raw percentage ÷ highest class percentage × 100.

The reference highest score must be positive and cannot be below the entered score. Multiplying all scores by the same factor preserves their ratios. It does not give every student the same point increase.

These transformations follow the methods discussed by David Richeson and corroborated in Omni Calculator’s formula guide. They are calculation choices, not universal school standards.

Worked examples

Square root

A raw score of 64% becomes 10 × √64 = 80.00%, an increase of 16.00 percentage points. A raw score of 50% becomes 70.71% after rounding.

Adding a bonus

Adding 10 percentage points to 95% gives 105.00%. If the cap is selected, the displayed result is 100.00% and the increase is 5.00 percentage points, with the original 105.00% disclosed.

Scaling against the highest score

A score of 60% with a highest class score of 80% gives 60 ÷ 80 × 100 = 75.00%, an increase of 15.00 percentage points. The student who scored 80% scales to 100.00%.

A curve is not a grading policy

This calculator explores individual score transformations. It does not fit a bell curve, assign class ranks, guarantee a passing grade, or decide letter-grade cutoffs. A mathematical transformation of scores does not necessarily make their distribution normal.

The curved result and its increase are each rounded to two decimal places from unrounded values. Subtracting the displayed original from the displayed result can therefore differ slightly from the displayed increase. Use the method, cap and rounding rule specified by your instructor.

Questions and answers

What does grading on a curve mean?

Grading on a curve means adjusting scores using a defined rule rather than leaving every raw percentage unchanged. The rule might add points, rescale a reference score, or use a root transformation. Those methods are different, so a raw score alone cannot identify your official adjusted grade.

How do I calculate a square-root curve?

Express the original score as a percentage, take its nonnegative square root, and multiply by 10. Equivalently, take the square root of the fractional score and multiply by 100. Do not take the square root of raw earned points unless the test maximum has been accounted for.

Is adding ten points the same as increasing a grade by ten percent?

No. Adding points to a percentage is an additive change in percentage points. A percentage increase multiplies the original percentage by a factor instead. This calculator uses percentage points in its addition method. Check the wording of your instructor's rule before entering a bonus or interpreting the result.

Will a curve always make my grade higher?

Not every grading policy guarantees an increase. The supported settings here are restricted to nonnegative bonuses, square roots of percentages between zero and 100, and scaling against a highest score no greater than 100. Under those restrictions, the calculated adjusted score cannot be lower than the original percentage.

Sources and maintenance

Maintained by Dennis Norton. Sources checked November 1, 2026. Course rules take precedence over these illustrative calculations.

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