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Grade Curve Calculator

Teachers curve scores in different ways. Enter a raw score, the class's top score and average, and see the curved result for the method you pick.

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Curved score

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Letter grade
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Points added
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Tips for using the grade curve calculator

  • Ask your teacher which method they use; it changes the result a lot for low scores.
  • A bell curve (fixed percentages of each letter) needs every score in the class, so it is not modelled here.
  • Use the final grade calculator to see what a curved test means for the course.

How the grade curve calculator works

A grade curve adjusts scores when a test turned out harder than intended. The three most common methods are:

Flat curve: New = Score + (100 − Highest score)
Square root: New = 10 × √Score
Mean shift: New = Score + (Target average − Class average)

A flat curve adds the same points to everyone so the top scorer gets 100. The square-root curve helps low scores most: 49 becomes 70 but 81 only becomes 90. Shifting the mean moves the whole class average to a target, such as a C+ or B−. Curved scores are capped at 100%. Letters use the standard 90/80/70/60 scale.

Worked example

You scored 72% on a test where the top score was 92% and the average 70%. A flat curve adds 8 points for 80% (B). The square-root curve gives 10 × √72 = 84.85% (B). Shifting the average from 70 to 78 also adds 8 points, giving 80%.

Frequently asked questions

What is a flat curve?

Every student gets the same number of points, usually enough to bring the top score to 100%.

How does a square root curve work?

Take the square root of the percentage and multiply by 10. It raises low scores more than high ones.

Can a curve lower my grade?

Flat and square-root curves cannot. Strict bell-curve grading can, if the class does well overall.

What is grading on a bell curve?

Assigning letter grades by rank so that set shares of the class get each letter.

Updated October 2026. Results are estimates for education, not financial or medical advice. All math runs in your browser; nothing you type is sent anywhere.

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