EU ring size 63 in US, UK & Japan
EU/ISO 63 denotes a nominal inner circumference of 63 mm. The nearest row in our chart is US 10.5, UK U½ and Japan 22: its calculated circumference is 63.4 mm and diameter is 20.17 mm. These are approximate chart equivalents, not identical dimensions.
- EU / ISO
- 63
- US / Canada
- 10.5
- UK / AU
- U½
- Japan
- 22
- CH / IT / ES
- 23
- Diameter
- 20.17 mm
- Circumference
- 63.4 mm
Under ISO 8653, the EU (and ISO) ring size number is the ring's inner circumference in millimetres. So EU 63 means the band measures about 63 mm all the way around — a circumference, not a diameter. That's why EU numbers are so much larger than US numbers for the same finger, and why an EU size can be read straight off a millimetre measurement.
Convert the other way with the EU to US ring size chart, open the US size 10.5 page, see the full chart, or use the converter.
Frequently asked questions
Why does EU 63 use a circumference number?
EU/ISO 63 follows the published circumference convention: about 63 mm around the inside (63.4 mm in this chart), corresponding to a 20.17 mm inner diameter.
How should I confirm EU 63 before ordering?
Check the retailer's own chart and confirm the 20.17 mm inner diameter with a physical sizer or a ring that already fits. Converted labels are a starting point, not a fit guarantee.
Values computed from the US jewellers’ diameter scale and cross-checked against ISO 8653 — methodology last reviewed 2026-08-27. Methodology