Ring Size Converter
Convert ring sizes between US, UK, and EU.
Ring sizes across regions
Ring sizing is regional: a US size 7 is roughly a UK O and an EU 54, all mapped from the inner circumference in millimetres. This lines up the common equivalents.
It is invaluable for buying a ring as a surprise or from an overseas jeweller, where a US 7, UK O, and EU 54 all describe the same finger but look nothing alike.
Measure, do not guess
Finger size changes with temperature and time of day, so measure warm and settled. The lookup happens on your device with nothing sent anywhere.
Frequently Asked Questions
How does the ring size converter work?
Ring sizes are converted through inside diameter. A US size 7 is about 17.3 mm inside diameter and approximately UK N 1/2.
When should I use this tool?
Use it to compare US, UK, EU, and millimeter ring measurements before resizing or ordering.
What is the main limitation?
Finger swelling and band width affect fit; confirm with a physical ring sizer for expensive rings.
Is this converter private?
Yes. It runs entirely in your browser, so your values are not uploaded or stored.
More free browser utilities for conversion, formatting, and technical cleanup.