Ellipse Properties Calculator

Summary

Enter semi-major and semi-minor axes to instantly compute area, perimeter, eccentricity, focal distance, and semi-latus rectum.

How it works

1. Enter the semi-major axis (a) — the longest radius of the ellipse.
2. Enter the semi-minor axis (b) — the shortest radius. b must be ≤ a.
3. All properties update instantly as you type.
4. Area uses the exact formula π·a·b.
5. Perimeter uses Ramanujan's second approximation for high accuracy.
6. Eccentricity, focal distance, and semi-latus rectum are derived from a and b.

Use cases

• Verify ellipse geometry for engineering drawings and CAD models.
• Calculate orbital parameters for astronomy and physics problems.
• Find the perimeter of an elliptical track or garden bed.
• Check eccentricity to determine how circular or elongated an orbit is.
• Compute the semi-latus rectum for conic section proofs.
• Use in optics to locate the focal points of an elliptical reflector.

Frequently Asked Questions