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Grade Curve Calculator
See what a curve does to a test score. Enter the raw score and choose a method — flat points added to everyone, scaling so the top score becomes 100%, or the square-root curve — to get the curved percentage and letter grade.
- Curved letter grade
- C+
- Raw score
- 72%
- Gain from the curve
- 5 points
Saved setups
Save a set of inputs you reuse — your usual rate, your loan, your room sizes — and load it back in one tap.
Your recent calculations
Results you calculate here are kept on this device so you can come back to them.
Formula
How to use it
- Enter the raw score and the points possible.
- Choose the curve method.
- Enter the points added or the highest score in the class, if the method needs it.
- Compare the curved score with the raw one.
Worked examples
A 72 out of 100 with 5 points added
- Curved score
- 77%
- Curved letter grade
- C+
- Raw score
- 72%
- Gain from the curve
- 5 points
A 72 when the highest score in the class was 90
- Curved score
- 80%
- Curved letter grade
- B−
- Gain from the curve
- 8 points
32 out of 50 (64%) on the square-root curve
- Curved score
- 80%
- Raw score
- 64%
- Gain from the curve
- 16 points
How the three methods differ
A flat curve gives everyone the same boost. Scaling to the top score helps in proportion to your score, so stronger scores gain more points. The square-root curve does the opposite: it lifts low scores the most — a 49 becomes 70, a 64 becomes 80, an 81 becomes 90 — while 100 stays 100.
What this does not do
“Grading on a curve” can also mean ranking students against a bell curve so that fixed shares of the class get each letter. That depends on the whole class’s scores, not just yours, and is not covered here.
Questions people ask
What is a 64 on a square-root curve?
10 × √64 = 80%.
If the highest score was 90, what does my 72 become?
72 ÷ 90 × 100 = 80%.
Can a curve lower my grade?
None of these three methods can; each leaves your score the same or higher. A flat curve can push scores above 100%, which instructors usually cap.