About this tool

A focused reference for an elliptical outline.

Ellipsepin does one job: turn your full ellipse dimensions into centre-based coordinates and a fixed-end string reference.

The calculator is free to use without an account. The outline, focus positions and local reports are calculated in your browser. It is designed for understanding and preparing a craft or workshop layout, with its assumptions visible beside the results.

What the numbers mean

Entered decimal dimensions are retained as exact rational millimetre values. The axes, working segment and entered-allowance addition can therefore be reported exactly. The focus offset needs a square root and is labelled approximate. Equal-axis classification uses the retained exact inputs, including after unit changes.

The diagram, SVG and coordinates use an ideal flat geometric model. They do not account for pin size, string stretch, pencil offset or fabrication tolerances. Ellipsepin provides no structural or cutting certification.

Free access and site support

The tool has no paid calculation tier. Advertising may support this website in the future. Its publisher metadata and ads.txt are prepared, but this host currently has no active advertising, consent-management or analytics loader. No advertising approval, ad serving or income is claimed.

See the original guide for worked examples and the primary mathematical reference, and privacy information for hosting and local export details.

Corrections and contact

If a number or explanation looks wrong, please include the dimensions, selected unit and the output you expected. Do not send confidential workpiece information. The contact page uses the portfolio's existing verified public forwarding address.