Geometry & Shapes
Ellipse Calculator
Ellipse — it uses area = π·a·b from the two semi-axes a and b. This page runs that same calculation on your numbers, in your browser: no signup, no uploads, nothing stored.
Want to find an ellipse's area and perimeter? Ellipse Calculator does it from your semi-major axis and semi-minor axis and shows the area and approximate perimeter clearly, with everything calculated in your browser.
About this calculator
It uses area = π·a·b from the two semi-axes a and b. That is the whole of the calculation — the mistakes happen in the inputs. It matters whenever a shape has to be measured, cut, covered or compared and the geometry has to be right first. Worked example: An ellipse with semi-axes a=5, b=3 has area = π × 5 × 3 = 47.12 . Use the calculator with your own figures; it runs entirely on your device.
How to use
- Enter the semi-axis a (half the longer axis).
- Enter the semi-axis b (half the shorter axis).
- Press Calculate to find the ellipse's area and perimeter.
- Read the area and the approximate perimeter.
Why use Ellipse Calculator
Fast
Calculations run in your browser. No round trip to a server.
Private
Your inputs never leave your device. Nothing is uploaded.
Free
No signup, no paywall, no ads-in-results, no watermarks.
Accurate
Uses standard formulas where applicable; check critical results before relying on them.
Mobile-ready
Optimised for phones, tablets, and desktops alike.
Transparent
Honest disclaimers wherever browser limits or regional rules apply.
Common uses
Use it for craft and woodworking projects
Use it when planning a garden bed
Use it for flooring and tiling estimates
Use it for fencing and edging lengths
Use it when checking a homework answer
Use it for sign and panel sizing
Technical notes
Ellipse Calculator uses area = π·a·b from the two semi-axes a and b.
Results assume exact, idealised shapes; real-world measurement error is not included.
Nothing you type is uploaded — the calculation happens entirely on your device.
FAQ
How is the area of an ellipse calculated?
The area is pi times a times b, where a and b are the two semi-axes.
Why is the perimeter only approximate?
An ellipse perimeter has no simple exact formula, so this tool uses Ramanujan's well-known close approximation.
What if I enter a negative axis?
Semi-axes must be positive, so the calculator asks you to correct any zero or negative value.
Does the Ellipse Calculator send my data to a server?
No. The Ellipse Calculator runs entirely in your browser, so nothing you enter is uploaded, stored, or shared.
Worked example
An ellipse with semi-axes a=5, b=3 has area = π × 5 × 3 = 47.12.