Square Root Curve Calculator
Curve grades with the square-root method: new score = √(old score) × 10.
Updated · How we check our maths
- Class average after curve
- 83.9%
- Average before
- 71.2%
- 64
- 80.0% (+16.0)
- 72
- 84.9% (+12.9)
- 81
- 90.0% (+9.0)
- 49
- 70.0% (+21.0)
- 90
- 94.9% (+4.9)
Quick answer
The square root curve replaces each percentage score with √score × 10. A 64 becomes 80, a 49 becomes 70 and an 81 becomes 90, while 100 stays 100. Low scores gain the most points, so it helps struggling students without pushing anyone above 100%.
What the Square Root Curve Calculator does
Paste one score or a whole column of scores. The calculator converts each to a percentage, takes the square root and multiplies by 10, then shows the curved score and the points added, plus the class average before and after.
Because the curve is steep at the bottom, it can lift failing grades a long way (a 36 becomes a 60). Many teachers prefer it because the order of students never changes and the top score is untouched.
The formula
Curved % = √(raw %) × 10
Worked example
A student scores 58/80 = 72.5%. √72.5 = 8.51 → 85.1%, a gain of 12.6 points.
How to use the Square Root Curve Calculator
- Paste the scores (separated by new lines, commas or spaces).
- Change the points possible if the test was not out of 100.
- Read each curved score and the new class average.
Frequently asked questions
Is the square root curve fair?
It keeps the ranking of students and never exceeds 100%, but it helps low scores far more than high ones — decide whether that matches your goal.
What does a 50 become with a square root curve?
√50 × 10 = 70.7%.
What other ways are there to curve grades?
Adding a flat number of points, scaling so the top score becomes 100, or bell-curve methods based on the mean and standard deviation.
Results are estimates for planning and learning. Check important figures with a qualified professional. How we build and check our calculators.