Grade Curve Calculator
A grade curve calculator for teachers: paste the class's scores, choose a curve, and see every curved score, the new average and the letters.
Result
Class average after the curve
88.86%
Average 76.86% → 88.86%: +12 points to every score.
Before → after
- Class average before
- 76.86%
- Top score after
- 100%
- Lowest score after
- 74%
Class
- Scores counted
- 7
- Scores capped at 100%
- 0
Worked out in your browser. Nothing you type is sent to us.
The working
Average 76.86% → 88.86%
| Original | Curved | Change | Letter |
|---|---|---|---|
| 62% | 74% | +12 | C |
| 71% | 83% | +12 | B |
| 75% | 87% | +12 | B |
| 78% | 90% | +12 | A |
| 80% | 92% | +12 | A |
| 84% | 96% | +12 | A |
| 88% | 100% | +12 | A |
How do you curve test scores?
Pick a rule and apply the same rule to every score. The simplest adds points so the top score reaches 100. In the example above, the top score was 88%, so the curve is +12 points to every score, and the class average moves from 76.86% to 88.86%.
The four curves
- Add points (flat): add (target − top score) to every score. Everyone gets the same number of points. curved = score + (target − top score)
- Scale (linear): multiply every score by target ÷ top score. Higher scores gain more points than lower ones. curved = score × target ÷ top score
- Square root: take the square root of the score and multiply by 10. Low scores gain the most, a 100 stays 100, and nothing goes over 100. curved = 10 × √score
- Shift the average: add (target average − class average) to every score, so the class average lands on your target. curved = score + (target average − class average)
The table under the calculator lists each original score, its curved score, the change and the new letter.
Which curve is fairest?
There is no official rule: it is the teacher's call, and many schools leave it to each class. Adding points keeps the gaps between students the same. Scaling and the square root curve help low scores more. Whatever you choose, tell students which curve you used, and apply it to the whole class.
Before you curve
Grade each test first with the test grade calculator. The scores never leave your browser: nothing you paste here is sent to our server.
Percentages to letter grades
College Board 4.0 chart (A 90–100, B 80–89, C 70–79, D 65–69)
| Grade | Percent | Grade points |
|---|---|---|
| A | 90–100 | 4.0 |
| B | 80–89 | 3.0 |
| C | 70–79 | 2.0 |
| D | 65–69 | 1.0 |
| F | below 65 | 0.0 |
Source: College Board BigFuture: How to Convert Your GPA to a 4.0 Scale, checked October 18, 2026. College Board calls this one commonly used system and says your school may differ. Its chart lists D as 66–69 and E/F as below 65, which leaves 65 itself unassigned; we count 65 as a D. The chart has no plus or minus grades, so B+ counts as a B on this scale.
10-point scale (A 90–100, B 80–89, C 70–79, D 60–69), as used statewide in North Carolina
| Grade | Percent | Grade points | Honors | AP / IB / college |
|---|---|---|---|---|
| A | 90–100 | 4.0 | 4.5 | 5.0 |
| B | 80–89 | 3.0 | 3.5 | 4.0 |
| C | 70–79 | 2.0 | 2.5 | 3.0 |
| D | 60–69 | 1.0 | 1.5 | 2.0 |
| F | below 60 | 0.0 | 0.0 | 0.0 |
Source: Onslow County Schools (NC): Grading Scale, under NC State Board of Education policy GRAD-009, checked October 18, 2026. Quality points: standard A 4, B 3, C 2, D 1, F 0; honors add 0.5; AP, IB and college (CCP) courses add 1.0; an F earns 0 at every level. Weights: Source: NC Department of Public Instruction: AP/IB/CIE Coursework, checked October 18, 2026. "The state course weighting system awards the equivalent of one (1) quality point to the grade earned in an AP/IB/CIE course." The 0.5 honors weight is from the Onslow County table above.
Plus/minus scale (A 93–100, A- 90–92 … D- 60–62), as used by Green Bay Area Public Schools, Wisconsin
| Grade | Percent | Grade points |
|---|---|---|
| A | 93–100 | 4.0 |
| A- | 90–92 | 3.67 |
| B+ | 87–89 | 3.33 |
| B | 83–86 | 3.0 |
| B- | 80–82 | 2.67 |
| C+ | 77–79 | 2.33 |
| C | 73–76 | 2.0 |
| C- | 70–72 | 1.67 |
| D+ | 67–69 | 1.33 |
| D | 63–66 | 1.0 |
| D- | 60–62 | 0.67 |
| F | below 60 | 0.0 |
Source: Green Bay Area Public Schools (WI): Grading Scale, checked October 18, 2026. Green Bay gives the plus and minus grades in thirds of a point (A- 3.67, B+ 3.33); many schools round these to 3.7 and 3.3, so check your own handbook. F* (fail, no credit), P (pass), INC (incomplete), MX (medical excuse) and NG (no grade) are not counted in GPA. The page sets no honors or AP weighting: the weighting boxes in the calculator are your school's rules. Not counted in GPA: F*, P, INC, MX, NG.
Questions students ask
Can a curve lower anyone's grade?
What happens to scores over 100%?
Can I paste scores from a spreadsheet?
Sources and method
- College Board 4.0 chart (A 90–100, B 80–89, C 70–79, D 65–69). Source: College Board BigFuture: How to Convert Your GPA to a 4.0 Scale, checked October 18, 2026. College Board calls this one commonly used system and says your school may differ. Its chart lists D as 66–69 and E/F as below 65, which leaves 65 itself unassigned; we count 65 as a D. The chart has no plus or minus grades, so B+ counts as a B on this scale.
- 10-point scale (A 90–100, B 80–89, C 70–79, D 60–69), as used statewide in North Carolina. Source: Onslow County Schools (NC): Grading Scale, under NC State Board of Education policy GRAD-009, checked October 18, 2026. Quality points: standard A 4, B 3, C 2, D 1, F 0; honors add 0.5; AP, IB and college (CCP) courses add 1.0; an F earns 0 at every level.
- Course weights. Source: NC Department of Public Instruction: AP/IB/CIE Coursework, checked October 18, 2026. "The state course weighting system awards the equivalent of one (1) quality point to the grade earned in an AP/IB/CIE course." The 0.5 honors weight is from the Onslow County table above.
- Plus/minus scale (A 93–100, A- 90–92 … D- 60–62), as used by Green Bay Area Public Schools, Wisconsin. Source: Green Bay Area Public Schools (WI): Grading Scale, checked October 18, 2026. Green Bay gives the plus and minus grades in thirds of a point (A- 3.67, B+ 3.33); many schools round these to 3.7 and 3.3, so check your own handbook. F* (fail, no credit), P (pass), INC (incomplete), MX (medical excuse) and NG (no grade) are not counted in GPA. The page sets no honors or AP weighting: the weighting boxes in the calculator are your school's rules.
- Formulas. The four curves are the formulas stated above, applied to every score as entered; averages are plain means. Which curve to use is the teacher's or school's choice, not a fixed rule.