Teachers & educators
Grade curve calculator.
Paste the raw scores, pick a curve, and see every curved score with the new class average and how many hit the cap.
Inputs
Result
Enter your numbers.
How do I curve test scores?
There is no single official grade curve. These are the common classroom methods, and each is plain arithmetic. Add points: curved = raw + points. Top to maximum (add): curved = raw + (maximum − highest score). Top to maximum (scale): curved = raw × maximum ÷ highest score. Square root: curved = maximum × √(raw ÷ maximum), which is 10×√raw on a 100-point test. Bell curve: curved = target mean + (raw − class mean) × target SD ÷ class SD, using the population standard deviation of the scores you pasted. Any result above the maximum is held at the maximum and any result below 0 is held at 0, and the tool counts those.
Worked example. On a 100-point test, a raw 64 becomes 80 under the square root curve, a raw 25 becomes 50, and 0 and 100 do not move. Adding 5 points turns a 98 into 100 (capped), not 103.
Frequently asked questions
How do you curve a test by adding points?
Add the same number of points to every raw score and cap the result at the maximum. The tool shows how many scores hit the cap.
How does a square root curve work?
The curved score is the maximum times the square root of raw divided by maximum. On a 100-point test a 64 becomes 80. Low scores gain the most and the order of students never changes.
What is the difference between adding points and scaling to the top score?
Adding shifts everyone up by the same amount. Scaling multiplies, so higher scores gain more points than lower ones.
What does a bell curve do to my scores?
It re-centres the scores on the target mean and stretches or squeezes the spread to the target standard deviation, keeping the order. It does not force a fixed share of A or B grades.
Should I curve at all?
That is a policy and fairness decision for you and your school. This page only does the arithmetic.
Sources
Checked
The curve formulas are common classroom practice, not a published standard. Standard deviation is the NIST definition. Runs entirely in your browser. Nothing you type is sent or stored.
Scope
Curving practices and whether curving is allowed are set by your school, department or course policy. Arithmetic only, not professional advice.