Is the ring size converter free?

Yes, completely free with no signup and no usage limits.

Does my data leave my device?

No. All conversions run in JavaScript inside your browser. Nothing is sent to any server.

Yes. The tool is mobile-first and works on iPhone Safari and Android Chrome.

US・UK・EU（周囲）・JP規格間でリングサイズを変換、または直径から算出します。

System Size

Or measure from diameter / circumference

Diameter (mm) Circumference (mm)

Select a sizing system and choose your ring size to see all equivalents.
Or measure the inside diameter or circumference of an existing ring in millimetres and enter it below.
The closest standard size in all systems is shown instantly.

Is the ring size converter free?: Yes, completely free with no signup and no usage limits.
Does my data leave my device?: No. All conversions run in JavaScript inside your browser. Nothing is sent to any server.
Does it work on mobile?: Yes. The tool is mobile-first and works on iPhone Safari and Android Chrome.

Last updated: 2026-05-20 By jarvisbox