Ring Size Converter
Convert ring sizes between the US number system, UK letters, and the inner diameter or circumference in millimeters — handy for buying a ring or a surprise gift.
How to use
Pick the system you know (US size, diameter, or circumference in mm) and enter the value. The tool shows the matching US, UK and millimeter sizes.
To find a size, measure the inner diameter of a ring that already fits, in millimeters, and enter it — that's the most reliable input.
FAQ
How do I measure ring size at home?
Measure the inner diameter of a ring that fits well, in millimeters, or wrap a strip of paper around the finger and measure the circumference.
Is EU ring size the same as circumference?
Roughly — the common EU/ISO size equals the inner circumference in millimeters, which is why we show both.
Are these exact?
They're standard reference values; jewelers may round differently. For an expensive ring, confirm with a jeweler.
Does it upload anything?
No — it all runs in your browser.