Grading Curve Calculator

When a test comes back harder than expected, a teacher may curve it: apply one rule to every score in the class. This calculator applies the three most common curves to a list of scores, shows each student’s new score, and tells you what the class average becomes. Add your own score to see where you land.

How to Use It

1. Choose a curve: Flat, Square Root or Target Average.
2. Paste or type the Class Scores, each out of 100.
3. For a flat curve, enter the Points to Add. For a target-average curve, enter the Target Class Average.
4. Optionally, enter Your Score to see your curved score.
5. Press Calculate to see the new class average and a table of every score before and after.

How It Works

A flat curve adds the same number of points to every score, so the gaps between students stay the same.

A square root curve takes the square root of each score and multiplies by 10:

Low scores gain the most, and 100 stays 100.

A target-average curve finds the one number of points that lifts the class average to your target, then adds it to everyone:

No score goes above 100. When a high score would, the calculator adds a little more to the rest so the average still reaches the target. If the class already meets the target, nothing changes.

Worked Example

Eight students scored 52, 61, 64, 70, 73, 78, 85 and 91, a class average of 71.75%.

• Flat, 5 points: every score rises by 5, and the average becomes 76.75%.
• Square root: the 52 becomes $\sqrt{52} \times 10 \approx 72.1$ (about 20 points more), while the 91 becomes about 95.4 (under 5 more).
• Target average of 75%: $75 - 71.75 = 3.25$ points are added to everyone.

Tips and Common Mistakes

• Use raw scores out of 100. Convert points to percentages first; a 42 out of 50 is 84.
• Include every student. Leaving scores out changes the class average, and with it a target-average curve.
• Square root helps low scores most. It’s generous to a struggling class but barely moves the top.
• A bell curve is different. It hands out letter grades by rank; the curves here raise scores instead.
• Ask how your teacher curves. The syllabus or teacher decides the method; this calculator shows what each one would do.