ExamTally → Grade Curve Calculator
Grade Curve Calculator
Apply a flat add, square-root, or scale-top-to-100 curve to a raw score — ExamTally stamps the curved percentage and letter grade.
To curve a grade, transform the raw score by the chosen method: add a flat number of points, take √(score) × 10, or rescale so the top score becomes 100. A raw 64% under a square-root curve becomes √64 × 10 = 80%, a B. Enter your raw score below.
Key takeaways
- Square-root: curved = √(raw) × 10. Lifts low scores most.
- Flat add: curved = raw + points, capped at 100.
- Scale to 100: curved = raw ÷ top score × 100.
- Letters use the default US scale (A 90+, B 80+, C 70+, D 60+, F < 60).
- Curving is optional — confirm the method your teacher actually uses.
How the grade curve calculator works
A curve maps your raw score onto a higher curved score using a fixed rule. This calculator supports the three most common rules. Each result is capped at 100% so no curve can produce an impossible grade.
The square-root curve is self-adjusting: it lifts a 36 to a 60 but a 81 only to a 90, so weaker scores benefit most while a perfect paper stays at 100. The flat add is the simplest — the same boost for everyone — while the scale-to-100 method stretches every score relative to the best paper in the room.
Worked example: 64% with a square-root curve
Take a raw score of 64%. The square root of 64 is 8, and 8 × 10 = 80%. That moves the grade from a D to a B. For comparison, a flat +10 would give 74% (a C), and scaling to a top score of 80% would give 64 ÷ 80 × 100 = 80% (also a B).
Standard A–F grading scale
| Letter | Percentage | GPA points (4.0) |
|---|---|---|
| A | 90–100% | 4.0 |
| B | 80–89% | 3.0 |
| C | 70–79% | 2.0 |
| D | 60–69% | 1.0 |
| F | Below 60% | 0.0 |
This is the most common US scale. Your school may use plus/minus grades or different cutoffs — always confirm.
Need the raw score first? Use the test grade calculator or percentage grade calculator, then bring the result here to curve it.
Frequently asked questions
What is a grade curve?
A curve adjusts raw test scores upward, usually because a test was harder than intended. Common methods are adding a flat number of points to everyone, taking the square root of the score and multiplying by 10, or scaling so the highest score in the class becomes 100%.
How does the square-root curve work?
The curved score is the square root of the raw percentage, multiplied by 10. A 64% becomes √64 × 10 = 8 × 10 = 80%. It lifts low scores a lot and high scores very little, and a perfect 100 stays 100.
How does the scale-top-to-100 curve work?
Find the highest raw score in the class and divide every score by it, then multiply by 100. If the top score was 80%, your 72% becomes 72 ÷ 80 × 100 = 90%. Everyone is rescaled so the best paper sets the new ceiling.
Which curve is most generous?
It depends on the score. For low marks the square-root curve usually gives the biggest lift; for scores near the top of the class the scale-to-100 method helps most. A flat add helps every score by the same fixed amount.
Can a curve ever lower my grade?
These three curves never lower a score — each result is capped at 100% and is at least as high as the raw score for a flat add or square-root method. The scale-to-100 method assumes the top score is below 100; if it is already 100, scores are unchanged.
Does my teacher have to use one of these curves?
No. Curving is at the instructor’s discretion, and many never curve at all. Some use bell-curve grading, drop the lowest question, or set custom cutoffs. Treat these results as estimates and confirm the actual method with your teacher.
The curve methods are standard mathematical transformations: square-root scaling (√score × 10), a constant additive curve, and linear rescaling to the top score. Letter-grade bands use the common US scale (A 90+, B 80+, C 70+, D 60+, F below 60); whether and how to curve is at each instructor’s discretion.
Last reviewed 2026-06-28