Calculate the area of an ellipse and an approximation of its perimeter from the two semi-axes.
| Area | – |
| Perimeter (approx.) | – |
Use this calculator to find the area of an ellipse and an estimate of its perimeter from the two semi-axes a and b. An ellipse is a stretched circle: a and b are half the full width and half the full height. If a equals b, the shape is a circle of radius a and both results are exact.
Area is π a b. The perimeter of an ellipse has no short closed formula; this calculator uses Ramanujan’s second approximation, which is accurate for typical ellipses and exact when a = b.
Use the same length unit for both semi-axes. Area is in that unit squared; the perimeter is a length.
Semi-axis a: Half the width of the ellipse.
Semi-axis b: Half the height of the ellipse.
Area: The interior of the ellipse, π a b.
Perimeter (approx.): Ramanujan’s second approximation of the circumference.
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