How do I measure ring size in mm?

Measure the inner diameter of a ring that fits across its widest point in millimetres, or wrap a strip of paper around your finger and measure the circumference. Enter either value to convert.

What is a US size 7 ring in UK?

A US size 7 is about a UK N½, an EU 54–55, an inner circumference of roughly 54.4 mm and a diameter near 17.3 mm.

Is anything uploaded?

No. The converter works entirely in your browser with no network requests.

Ring Size Converter

Convert ring sizes between US, UK, EU, circumference and diameter.

Ring size converter

Match ring sizes across regions and the physical measurements jewellers use: US/Canada, UK/Australia letters, EU, plus inner circumference and inner diameter in millimetres.

For the most accurate result, measure the inside diameter of a ring you already own and convert from there. All lookups happen locally in your browser — nothing is uploaded.