EU ring size 45 in US, UK & Japan

EU/ISO ring size 45 is an inner circumference of about 45 mm (45.5 mm exactly) — that equals US 3.5, UK G½ and Japan 5, with an inner diameter of 14.48 mm.

Illustrative — screen scale varies. Use the true-scale ring below for a real measurement.

EU / ISO: 45
US / Canada: 3.5
UK / AU: G½
Japan: 5
CH / IT / ES: 5
Diameter: 14.48 mm
Circumference: 45.5 mm

Why EU 45 looks larger than US 3.5

Under ISO 8653, the EU (and ISO) ring size number is the ring's inner circumference in millimetres. So EU 45 means the band measures about 45 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.

50 mm reference bar

True-to-scale ring Printed at 100%, the inside of this ring is 14.48 mm across.

Convert the other way with the EU to US ring size chart, open the US size 3.5 page, see the full chart, or use the converter.

Frequently asked questions

Why does EU 45 use a circumference number?

EU/ISO 45 follows the published circumference convention: about 45 mm around the inside (45.5 mm in this chart), corresponding to a 14.48 mm inner diameter.

How should I confirm EU 45 before ordering?

Check the retailer's own chart and confirm the 14.48 mm inner diameter with a physical sizer or a ring that already fits. Converted labels are a starting point, not a fit guarantee.