About Ring Size Calculator

A free, independent sizing toolkit built around one idea: millimetres don't lie, even when country charts disagree.

Last updated: November 2026

Ring Size Calculator exists because ring sizing is needlessly confusing: the same finger is a 7 in New York, N½ in London, 54 in Paris and 14 in Tokyo. Our tools convert everything through the shared measurement — inner diameter and circumference in millimetres — using the standard chart published on our ring size chart page.

Everything runs in your browser. The on-screen sizer, calculator and converter send nothing to a server, and calibration is stored only on your own device. We are not a jeweller and we do not sell rings; guides like how to measure ring size and engagement ring sizing exist to help you buy confidently elsewhere.

Honest note on charts: Ring size charts vary by up to half a size between jewellers. Always confirm your size in millimetres — inner diameter or circumference — with the jeweller you are buying from before you order.

Questions or corrections? See the contact page or browse the FAQ.