Ellipse

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All tools › Flat shapes

Ellipse

Area, focuses, eccentricity — and the perimeter nobody has a formula for.

It runs entirely in this browser tab: what you type is never uploaded, and the tool makes no network request while it works. Open your browser's network panel and try it — nothing leaves the page. There is no sign-up and no account.

How to use it

  1. Paste your text into the box above, or open a file.
  2. There is nothing to set: this tool does one thing.
  3. Copy the result, or save it as a file. The result updates as you type.

Questions

What unit are the answers in?
Whatever unit you typed. A length comes back in it, an area in the square of it and a volume in the cube. Nothing here names a unit or converts between two, because a calculator that converted silently is how a room comes out a hundred times too large.
Why does it refuse some measurements?
Because they do not describe a shape. Three sides only close into a triangle when any two are longer than the third; a hypotenuse is the longest side; a wall cannot be thicker than the pipe's radius. Each refusal says which condition failed and gives the numbers back.
Are the answers exact?
As exact as the shape allows, and the tool says where it is not. Nothing here uses floating point — every root, sine and logarithm is computed digit by digit — but π has no last digit and an ellipse's perimeter has no closed form at all, so those results say they are approximations and why.
Is what I type uploaded anywhere?
No. This page carries the whole tool as WebAssembly and runs it on your own device. Nothing you type is sent anywhere, and there is no network request to make while it works.

Other tools for flat shapes

Area
The area of eight flat shapes, with the formula and a sketch.

Perimeter
The distance round the edge, and where there is no exact one.

Trapezium
Four sides fix it, and the height follows from them.

All thirty tools