Grade Curve Calculator — Curve Test Scores 4 Ways

How to use the grade curve calculator

Paste the scores. Copy a column from your gradebook or spreadsheet, or type them separated by commas. Points like 41/50 are converted to percentages.
Pick a curve. Each method is explained below. For a target average, enter the class average you want.
Read the results. You get the new class average, every curved score with its letter grade, and how many students land in each letter before and after.

Students can use it too: enter your own score and the highest score in the class to see what a flat or scaled curve would do for you. A square-root curve only needs your own score.

Four ways to curve grades

1. Add points so the top score is 100

Curved = score + (100 − top score)

The most common classroom curve. Everyone gains the same number of points, so the gaps between students stay the same.

2. Scale so the top score is 100

Curved = score × (100 ÷ top score)

Every score is multiplied by the same factor. Higher scores gain a little more points than lower ones.

3. Square-root curve

Curved = 10 × √score

Doesn't depend on anyone else's score. It lifts low scores the most: 49 becomes 70, 64 becomes 80, and 100 stays 100. Useful when a test was hard for the whole class, including the top scorer.

4. Curve to a target average

Curved = score + (target average − class average)

Adds the points needed for the class average to hit a goal, such as 75% or 80%. If the class already averages above the target, no points are added.

The same test, curved four ways

Five students scored 58, 64, 72, 81 and 88 (class average 72.6%). Here is what each curve does to them:

Five test scores curved four different ways
Original	Add points	Scale to 100	Square root	Target average 80%
58% (F)	70% (C-)	65.9% (D)	76.2% (C)	65.4% (D)
64% (D)	76% (C)	72.7% (C-)	80% (B-)	71.4% (C-)
72% (C-)	84% (B)	81.8% (B-)	84.9% (B)	79.4% (C+)
81% (B-)	93% (A)	92% (A-)	90% (A-)	88.4% (B+)
88% (B+)	100% (A+)	100% (A+)	93.8% (A)	95.4% (A)
Average 72.6%	84.6%	82.5%	85%	80%

Worked example

Reading the table

The student with 58% (an F) gets a C- with the flat curve, a D with scaling, a C with the square root and a D with the target-average curve.

The top student reaches 100% with the two top-score methods, but 93.8% with the square root.

Choosing a curve as a teacher

Explain it before you apply it. Students accept a curve they understand. A flat curve is the easiest to explain.
Check the question, not just the class. If nearly everyone missed one item, dropping that question can be fairer than curving the whole test.
Be consistent. Use the same method for every section of the course.

Before you curve, the average grade calculator shows the class mean, and the EZ Grader turns a number wrong into a grade for any test length.

Frequently asked questions

How do you curve grades?

Pick a method and apply it to every score. The simplest is a flat curve: find the highest score, subtract it from 100, and add that many points to everyone. If the top score is 88, everyone gets 12 points.

Which grading curve is the fairest?

A flat curve treats everyone the same by adding equal points. Scaling to 100 rewards high scorers slightly more, and a square-root curve helps low scores most. Many teachers prefer a flat curve or a target average because they're easy to explain.

How much will the curve raise my grade?

Enter your score and the highest score in the class. With a flat curve you gain the gap between the top score and 100. With a square-root curve a 64 becomes an 80, while a 90 only becomes about 94.9.

Can a curve lower my grade?

Not with these methods. Each one only adds points or scales up, and this calculator never lowers a score. A true bell curve, where a fixed share of students gets each letter, can lower some grades, which is why few U.S. high schools use it.

Should curved scores go above 100%?

Usually not. Most teachers cap curved scores at 100%, which is this calculator's default. Turn the cap off if your teacher lets the curve count as extra credit.

What is a bell curve in grading?

It assigns letters by rank instead of score, for example the top 10% get an A and the next 20% a B, so grades follow a normal distribution. It's mostly used in large college courses and law school, not in typical high school classes.

Last reviewed October 28, 2026 by Muhammad Shahid. See how we calculate.