Written by Zufishan · MS Environmental Science · Updated June 2026
When instructors curve grades
A grade curve is a uniform adjustment instructors apply when a test was harder than intended or when the class average falls well below the expected target. The two most common forms are a flat point bump, where everyone's raw score increases by the same number of points, and a flat percentage bump, where everyone's percentage increases by the same amount. Both preserve relative ranking; they just shift the whole class up together.
The two curve modes
Points mode: Curved score = Original score + Curve points (capped at maximum)
Percentage mode: Curved percentage = Original percentage + Curve percentage (capped at 100%)
Worked examples
Points mode. Original score 72 out of 100, curve plus 5 points. Curved score = 77 out of 100 = 77%. Letter grade moves from C− to C+.
Percentage mode. Original score 72 out of 100 = 72%, curve plus 10%. Curved percentage = 82%. Letter grade moves from C− to B−. The same curve gives a larger absolute lift in percentage mode than points mode when the maximum is 100.
Understanding your result
| Original percentage | After +5 points curve | After +10% curve | Letter change (pts) |
|---|---|---|---|
| 58% (F) | 63% (D) | 68% (D+) | F to D |
| 68% (D+) | 73% (C) | 78% (C+) | D+ to C |
| 72% (C−) | 77% (C+) | 82% (B−) | C− to C+ |
| 85% (B) | 90% (A−) | 95% (A) | B to A− |
| 96% (A) | 100% (A+) | 100% (A+) | A to A+ |
How to use this calculator
- Choose Points or Percentage mode depending on how your instructor described the curve.
- Enter your original score and the maximum possible score.
- Enter the curve amount.
- Read the original and curved grades side by side in the result panel.
Other curve methods not covered here
Square-root curve. The new score equals the square root of the original score multiplied by the square root of the maximum. This gives a larger lift to low scores than to high ones, which compresses the distribution. It is less common but some instructors prefer it for very difficult tests.
Highest-score curve. The top score in the class becomes the new 100% and every other score is scaled proportionally. This is equivalent to a percentage curve sized to 100 minus the top score. For example, if the highest raw score was 88%, every score is multiplied by 100 divided by 88.
Bell curve grading. Grades are distributed against a target mean and standard deviation rather than a fixed scale. This requires class statistics and is best handled with the Class Average Calculator as a starting point.
When to use this calculator
Use it when an instructor announces a curve and you want to know your new grade before the gradebook updates. Use the Class Average Calculator first if you want to understand what curve size would push the class average to a target, then bring that number here to check your own result. Once you have the curved grade, feed it into the Course Grade Calculator to see how it moves your overall course standing.
Common mistakes
Mixing up points and percentage modes. A plus-10 in points mode on a 100-point test adds 10 percentage points. A plus-10 in percentage mode also adds 10 percentage points here, but on a 50-point test the same plus-10 in points mode adds 20 percentage points. Make sure you know which type your instructor announced.
Applying the curve to the wrong maximum. If the test was out of 80 points, enter 80 in the Max field, not 100. Using the wrong maximum will shift the percentage result incorrectly.
Expecting the curve to change all letter grade gaps equally. A 5-point curve near the B/A boundary might jump you a full letter grade. The same curve near the middle of a grade band changes nothing on the letter grade. Check the table above to see where your score sits relative to the boundaries.
Related calculators
- Class Average Calculator to find the class average and decide if a curve is warranted
- Assignment Grade Calculator to convert raw points to a percentage before applying a curve
- Course Grade Calculator to feed the curved grade back into the overall course total
- Extra Credit Calculator if you are looking to raise a grade through extra work rather than a curve
- Grade Calculator for your full weighted course grade
Disclaimer: Results are estimates based on the scores and curve you enter. Letter grades use the standard US plus-minus scale. Your instructor may cap curved scores differently or use a non-standard curve method. Always confirm your official curved grade with your instructor.