Grade Curve Calculator: Curve Your Scores Four Ways

Grade curve calculator: the quick answer

To curve a grade, change every score by one rule so the class does better, then regrade. Adding 5 points to the scores 52, 61, 68, 74, 79, 85 and 91 lifts the class average from 72.86% to 77.86%. Setting the top score to 100%, which multiplies every score by 100 ÷ 91, lifts it to 80.06%. A square root curve lifts it to 85.02%. The grade curve calculator above applies any of these to your own scores and shows each score before and after.

How to use the grade curve calculator

1. Type or paste the scores in the box. Add the points possible if they are points, not percentages.
2. Choose a curve method and fill in its number, such as the points to add.
3. Leave the cap on if no curved score may go above 100%.
4. Read the class average before and after, and how many scores move up a grade.
5. Check the table of every score to see exactly who is affected, then compare other methods.

Which curve method to use in the grade curve calculator

Add points raises every score by the same amount, so the gaps between students stay the same. It helps a low score as much as a high one, and the cap stops anyone passing 100%. Top score to 100% multiplies every score by the same factor, so higher scores gain more points than lower ones. It rewards the class when one question was too hard. Square root turns 100 into 100 and 64 into 80. It lifts low scores the most and leaves the top alone. Stretch gives a new lowest and highest score and spreads the rest evenly between them, so it can lift the bottom and the top by different amounts.

What the grade curve calculator does not do

This grade curve calculator changes scores by a fixed rule. It does not force a set share of students into each grade, which some teachers call a bell curve, and it does not decide whether a curve is fair. Whether to curve, and how, is the teacher’s choice. Check your course policy before you plan on one. A curve can also move a score down, for example when a stretch lowers the top score, and the calculator flags that when it happens.

Grade curve calculator formulas and a worked example

For the stretch, Low and High are the new lowest and highest scores you choose. Letters are decided on the exact value, not a rounded one. The full rules are on the grading methodology page.

Grades use the standard scale. For the top score method, 68 × 100 ÷ 91 = 74.73, which is a C. For the square root, 10 × √68 = 82.46, a B. For the stretch, 60 + (74 − 52) × 40 ÷ 39 = 82.56.

Choosing a grading scale

The standard and plus/minus scales are examples, not rules. If your school uses different cutoffs, choose Custom and enter them, or build and print a chart with the grading scale calculator.

Sources and further reading

Whether and how to curve is set by the teacher and the school, so follow your own grading policy. For background, see Norm-referenced test and Academic grading in the United States on Wikipedia.

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