Ellipse area, Ramanujan perimeter, eccentricity, and focal distance from the two semi-axes.. Ellipse Calculator is a free online tool from the ToolsRift Math Calculators collection. It runs entirely in your browser — nothing to install, no signup, and your data never leaves your device.
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How to use Ellipse Calculator
Enter the semi-major (a) and semi-minor (b) axes and the calculator returns area, perimeter, eccentricity and focal distance.
Frequently asked questions
How is the area of an ellipse found?
Area = π × a × b, where a and b are the semi-major and semi-minor axes.
Why use Ramanujan's perimeter formula?
An ellipse perimeter has no simple exact formula; Ramanujan's approximation is extremely accurate and fast to compute.
What is eccentricity?
A measure of how elongated the ellipse is: e = √(1 − b²/a²), where 0 is a circle and values near 1 are very stretched.
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