Grade Curve Calculator

It supports four common methods. The flat add curve raises the single highest score to the maximum and adds that same delta to everyone. The square root curve sets each score to the square root of its percent times ten, which lifts lower scores the most. The linear scale curve multiplies every score by one factor so the class mean lands on a target you choose. The bell curve converts each score to a z-score and remaps it onto a target mean and spread.

The calculator finds the top raw score, subtracts it from the maximum possible, and adds that constant to every score. For example, if the highest score is 90 out of 100, every score gains 10 points and the top student reaches 100. This preserves the gaps between students, so the spread stays the same and only the average shifts up.

The square root curve uses curved equals the square root of the raw percent times ten, so a 64 becomes 80 and an 81 becomes 90. Low and middle scores rise the most, while a perfect score stays unchanged. It is a good fit when a test was harder than intended and you want generous relief at the bottom without inflating the top.

The pass rate is the share of students at or above the passing score, which you set as a percentage of the maximum (60 by default). The calculator reports the pass rate both before and after the curve so you can see how many more students clear the line. With a 60 percent threshold on a 100 point test, anyone scoring 60 or higher counts as passing.

The bell curve divides each deviation by the class standard deviation to get a z-score. If every score is the same, the standard deviation is zero and that division is undefined, so the calculator returns no result. Enter at least two different scores, and add a target mean and target spread to control where the new distribution is centered and how wide it is.

This tool clamps every curved score to the range from 0 to the maximum possible, so a curve can never push a student above a perfect score or below zero. Scores are shown to one decimal place. Curving is a policy choice, so confirm the method and any caps against your school or course grading rules before posting final grades.