Ellipse Area Calculator
Enter the semi-major axis (a) and semi-minor axis (b) of an ellipse to get its area instantly, plus the perimeter using Ramanujan's approximation — with a step-by-step breakdown of every calculation.
How to use
- Enter the semi-major axis (a) — half of the longest width of the ellipse.
- Enter the semi-minor axis (b) — half of the shortest width — in the same unit.
- Read the result: area equals pi times a times b, plus the perimeter estimate.
- Open the steps section to see each part of the calculation worked out.
Good to know
- The area formula is pi times a times b — double either axis and the area doubles.
- A circle is just an ellipse with a equal to b.
- There is no exact simple formula for the perimeter, so Ramanujan's approximation is used.
- Keep both axes in the same unit (for example, centimetres).
Note: The famous Ramanujan approximation is used for the perimeter because there is no exact simple formula for the perimeter of an ellipse.