Enter any measurement — diameter, circumference, US size, or UK size — and instantly see your equivalent in every international sizing system.
Measure the inside width of a ring that already fits you — straight across the inside opening — using a ruler or digital calipers. Enter the measurement in millimetres below.
Wrap a strip of paper around the base of your finger, mark where it overlaps, then measure the marked length in millimetres. Enter that number below.
Enter your US ring size number below. Half sizes (e.g. 6.5) are supported. The converter will show your exact equivalent in all other international systems.
Select your UK letter size from the dropdown. UK sizes are used in the United Kingdom, Australia, New Zealand, and South Africa.
The EU size is the inner circumference of the ring in millimetres. Common EU sizes range from 44 to 71. Enter your EU size number below.
Click any row to highlight it. Your converted size will be highlighted automatically after converting.
| US | Diameter | Circumference | UK / AU | EU | Japan | Swiss |
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Step-by-step measurement methods, expert tips, average sizes, and FAQs — all in one place.
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