Ellipse Perimeter Calculator
Enter positive semi-major axis a and semi-minor axis b, with a ≥ b.
A QUICK WALKTHROUGH
How to use this tool
- Enter semi-major axis a.
- Enter semi-minor axis b.
- Review the Ramanujan II perimeter approximation.
Approximation
Uses Ramanujan’s second approximation: P≈π(a+b)[1+3h/(10+√(4−3h))], h=((a−b)/(a+b))². Exact ellipse perimeter generally requires an elliptic integral.
Input convention
Enter semi-axes, not full diameters, and require a≥b>0. Result is approximate and uses the input length unit.
GOOD TO KNOW
Common questions
Is this exact?
No. It uses a standard approximation; exact perimeter involves an elliptic integral.