Grade Curve Calculator: Full Guide (2025)
Use our grade curve calculator to fairly adjust class scores. Supports bell curve, square root, linear, and custom methods. Perfect for teachers and professors.
What is Grade Curving?
Curving adjusts raw scores to fit a desired distribution when a test is too hard or easy. Common in college courses.
1. Bell Curve (Normal Distribution)
Sets mean and standard deviation. ~68% get C, ~14% B/D, ~2% A/F.
Formula: Curved = μ + σ × z-score
2. Square Root Curve
Boosts low scores: Curved = √(raw) × 10
65 → 80.6, 88 → 93.8
3. Linear Scaling
Scales highest score to target (e.g., 100%): Curved = (raw / max_raw) × target
4. Custom Cutoffs
Set your own A/B/C thresholds after adjustment.
Example: Bell Curve
| Raw | Curved (Mean 75, SD 10) | Letter |
|---|---|---|
| 94 | 92.3 | A |
| 88 | 86.1 | A- |
| 72 | 74.2 | C |
| 65 | 68.9 | D+ |
| 55 | 60.1 | D- |
When to Curve?
- Class average < 70%
- Test too difficult
- Standardize across sections
Step-by-Step Guide
- Enter scores: Comma/space separated
- Choose method: Bell, sqrt, etc.
- Adjust settings: Mean, cutoffs
- Get results: Table + stats
Why Use This Calculator?
- 4 curve methods
- Letter grades
- Stats: mean, median, SD
- Free & instant
FAQ
Is curving fair?
Yes when test is flawed. Transparent policy helps.
Can I curve up only?
Yes. Set target mean > current average.
What if average is 85%?
Curve down or leave as-is. Use linear to cap at 100.
Pro Tips
- Use bell curve for large classes (>30)
- Square root for harsh grading
- Always show raw vs curved
- Combine with Weighted Grade Calculator
Conclusion
Ensure fair grading with our grade curve calculator. Adjust difficult exams and help students succeed. Curve now!
Related: Final Grade | Grade Distribution