Grade Curve Calculator
Curve a test for the whole class in seconds. Paste your scores, pick a curving method, and see every student's new percentage and letter grade.
Enter class scores
One score per student, separated by commas, spaces or new lines. No names needed.
Use 100 if your scores are already percentages.
Curved results
| # | Score | Before | After | Grade |
|---|
Letter grades use the example scale A 90, B 80, C 70, D 60. Rows stay in the order you entered.
How to curve grades
- Paste every student's score for the test, in any order.
- Enter the total possible points, or 100 if the scores are percentages.
- Choose a curving method and a target, then read the new percentages and letter grades.
The calculator runs entirely in your browser. Scores are not saved or sent anywhere.
Grade curving methods compared
Example: a test where the highest score is 88% and one student scored 64%.
| Method | Formula | 64% becomes | 88% becomes |
|---|---|---|---|
| Flat curve | score + (100 − highest) | 76% | 100% |
| Linear scale | score × 100 ÷ highest | 72.73% | 100% |
| Square root | 10 × √score | 80% | 93.81% |
| Target average (75%) | score + (75 − average) | depends on the class average | |
Flat curve (add points)
Every student gets the same number of points, chosen so the top score reaches the target. It is the easiest curve to explain to students and parents, and it keeps the gaps between students the same.
Linear scale (highest score becomes 100%)
Every percentage is multiplied by the same factor. A student who scored twice as much as another still scores twice as much after the curve, so higher scores gain more points.
Square root curve
Takes the square root of the percentage and multiplies by 10. It raises low and middle scores the most, never lowers a score, and needs no target. It is a common choice when a test turned out much harder than planned.
Target class average
Shifts every score by the same amount so the class average reaches a goal such as 75%. Useful when your school or department expects a certain average. If the cap is on, the final average can land a little below the target.
What about a bell curve? A strict bell curve assigns a fixed share of each letter grade (for example, only the top 10% get an A). It can lower some students' grades and is uncommon in K–12 classrooms, so this calculator doesn't use it.
Tips for curving fairly
- Decide on the method before you look at individual students' results, and use it for the whole class.
- Check for a single outlier: one very high score can make a flat or linear curve almost useless for everyone else.
- Tell students which method you used. A short note like "10 points were added to every score" avoids confusion.
- Keep the original scores in your gradebook notes in case you need to explain a grade later.
Frequently asked questions
What is the fairest way to curve grades?
There is no single fairest method. A flat curve adds the same points to everyone and keeps the gaps between students. Linear scaling rewards everyone in proportion to their score. The square root curve helps low scores the most. Choose the method that matches why the test needs curving, and apply it to the whole class.
How do I curve a test so the highest score is 100?
Use either the flat curve (add 100 minus the highest percentage to every score) or linear scaling (multiply every percentage by 100 ÷ the highest percentage). The first adds the same points to everyone; the second gives more points to higher scores.
How does the square root curve work?
Each curved percentage is 10 × √(original percentage). For example, 64% becomes 80% and 81% becomes 90%. It never lowers a score, keeps 0% and 100% unchanged, and raises low scores more than high ones.
How do I curve grades to a target class average?
Choose the Target average method and enter the average you want, such as 75%. The calculator adds the difference between the target and the current average to every score. With the 100% cap on, students at the top cannot go above 100%, so the final average can land slightly below the target.
Are student scores saved or sent anywhere?
No. The calculator runs entirely in your browser. Scores are not saved or sent anywhere, and you don't need to enter student names.
Related tools
- Easy Grader: turn one test score into a percentage and letter grade.
- Grading scale guide: letter-grade cutoffs and GPA.
- Final Grade Calculator: the score needed on a final exam.
- Printable grading charts for tests out of 5 to 100.