Ellipse Calculator
Find an ellipse's area, circumference and eccentricity.
Get all the key measurements of an ellipse from its two semi-axes.
The math behind it
Area is exactly πab. The circumference has no simple closed form, so we use Ramanujan's accurate approximation. Eccentricity √(1 − b²/a²) measures how stretched it is.
Worked example
a = 5, b = 3 → area ≈ 47.12, circumference ≈ 25.53, eccentricity ≈ 0.8.
FAQ
What does eccentricity 0 mean?
A perfect circle; as it approaches 1 the ellipse gets more elongated.