Grade Curve Calculator

How to use

1. 1Pick Single score or Class roster, then choose a curve method from the five options.
2. 2Set the maximum points and decimal precision. Then enter the method-specific inputs: a flat bonus, a target top score, or a target class mean for the optional bell-curve shift.
3. 3In Single score mode, type the raw score. For scale-to-max or shift methods, also enter the highest score in the class. For the bell curve, enter the class mean and standard deviation.
4. 4In Class roster mode, paste one score per line. Optionally include a name before the score, separated by a space, comma, or colon.
5. 5Read the curved score, letter grade, before-and-after statistics, and the letter grade distribution. Use Copy summary or Copy roster CSV to export the result.

About this tool

Grade Curve Calculator applies a grading curve to a single test score or to a full class roster, entirely in your browser. Choose between five common methods. A flat curve adds a fixed bonus to every score. Scale to maximum stretches all scores linearly so the highest score becomes the chosen target, typically 100. Shift highest to top finds the gap between the top score and the target and adds it to everyone. The square root curve, popular when an exam was harder than expected, maps each score to the square root of its percentage times ten, only raising scores. The bell curve uses the class mean and population standard deviation to assign letter grades by sigma bands, with an optional shift that moves the class mean to a target value. In roster mode you can paste plain scores (one per line) or names alongside scores separated by spaces, commas, or colons. The tool reports the mean, median, minimum, maximum, and standard deviation before and after the curve, the letter grade distribution across A through F, and a per-student table you can copy as CSV. Curved scores are capped at the maximum points and rounded to the precision you set. Nothing is uploaded, no account is required, and the math is fully transparent so teachers and students can verify it against any grading policy.

Free to use. Works in your browser. No signup, no login.