About Quick Ring Size
A ring sizer that measures on the screen, prints at true size, and converts between every common system, with no account and nothing to sell you.
What it is
Quick Ring Size is a free tool for finding a ring size and converting it between US, UK, EU, and Japan. You can measure a ring you own directly on the screen after a quick calibration, print a paper sizer that survives 100% scale printing, or type a millimetre measurement and read the size.
It is not attached to a jewelry store. There is no size that happens to match a product we want to sell, because we do not sell rings. The tool gives you the measurement and the sources behind it, and leaves the buying to you.
How it works
Everything runs in your browser. The conversion math and the calibration are plain client-side code, which is why the tool works offline once loaded and why your measurement never leaves the page. The conversion table is built from the ISO 8653 standard and published charts; the full sourcing is on the methodology page.
On-screen measuring depends on calibrating to a physical reference, because screens vary in pixel density. We use a standard bank card, which is the same size worldwide. The result is a close estimate, good for buying, though for an engagement ring it is worth confirming with a jeweler.