TidyToolsThe three curves, and what each one does to you
“Curving” is not one procedure. Professors use several, and they benefit very different students, so it is worth knowing which one you are getting.
1. Flat curve — add points to everyone
The simplest and by far the most common: the instructor adds a fixed number of points to every score. A 64 with a 5-point curve becomes a 69. It is transparent and it shifts the whole class equally, which means it never changes anyone’s rank. If you were last before the curve you are still last, just with a better number.
2. Scale to the highest score
The top score in the class is treated as 100% and everything else is scaled up in proportion: curved = raw × 100 ÷ top score. If the best mark was 88, your 64 becomes 64 × 100 ÷ 88 = 72.7. This one rewards you most when the highest score is low, which is the point — it is a signal that the exam, not the class, was the problem. Note it is multiplicative, so strong students gain more raw points than weak ones.
3. Square root curve
Your score is square-rooted and multiplied by ten: curved = √raw × 10. A 64 becomes √64 × 10 = 80. This is the most generous curve at the bottom and the least generous at the top — a 36 leaps to 60, while a 90 only reaches 94.9. It compresses the class upward and is used when an instructor wants to rescue failing students without handing the top of the class free marks.
Which curve helps you most?
If you scored below the class average, the square root curve is almost always your best outcome. If you scored near the top, scaling to the highest score usually beats it. A flat curve treats everyone identically and is the only one of the three that cannot change who is ahead of whom.
One caveat worth knowing: a real “curve” in the strict statistical sense means fitting grades to a normal distribution with fixed percentages of each letter — say the top 15% get an A regardless of their raw score. That version can lower your grade, and no calculator can predict it because it depends entirely on how everyone else did. The three methods above are the ones that only ever help.
Frequently asked questions
Can a curve lower my grade?
The three methods on this page can only raise a score or leave it unchanged. But a true statistical curve, where a fixed percentage of the class receives each letter grade, can lower it — if you scored above average on an easy exam you may still land a B. That kind of curve depends on the whole class distribution and cannot be calculated from your score alone.
What is the square root curve?
Take the square root of your score and multiply by ten. A 64 becomes 80, a 49 becomes 70, and a 90 becomes about 94.9. It lifts low scores much more than high ones, so it is the most generous curve if you are near the bottom.
Does a flat curve change class rankings?
No. Adding the same number of points to everyone shifts all scores equally, so the order is identical. Only the numbers change.
Do curved scores get capped at 100?
Usually yes — most instructors cap the result at 100%, and this calculator does the same. A few allow scores above 100 when a curve pushes a top student past the maximum, so check your syllabus if it matters.