Grade Curve Calculator
Got a test that came out too hard? 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. Students stay in the same order you pasted them.
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.
Everything is worked out inside your browser, and the scores you paste are never stored or sent.
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
The new score is √(old percent) × 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 curve to use?
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. Low scores gain the most from the square root curve. Choose the method that matches why the test needs curving, and apply it to the whole class.
How can I curve a test so the top score becomes 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.
What happens to scores under a square root curve?
Each curved percentage is 10 × √(original percentage). So 64% turns into 80%, and 81% turns into 90%. It never lowers a score, keeps 0% and 100% unchanged, and raises low scores more than high ones.
How can I curve grades to hit a set 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. All the math happens in your browser, nothing is stored or sent, and you never have to type 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: what a student must score on the final to reach a goal grade.
- Printable grading charts for tests out of 5 to 100.