* Ring size conversion
UK W½ ring size conversion
UK W½ is an inside diameter of 21 mm (circumference 65.9 mm). In other systems that is US 11.5 = UK W½ = EU 66 = Japan 25.
Published July 11, 2026
UK W½ — full conversion
- Inside diameter
- 21 mm
- Inside circumference
- 65.9 mm
- Japan
- 25
- US / Canada
- 11.5
- UK / Australia
- W½
- EU (ISO)
- 66
Nearby sizes
- Ø 20.6 mm — US 11 = UK V½ = EU 65 = Japan 24
- Ø 21.4 mm — US 12 = UK X½ = EU 67 = Japan 26
Buying tips for UK W½
- Wide bands feel tighter — consider going up ~½ US size for bands over 6 mm.
- Printable paper sizers are often ¼–½ size off; prefer a metal gauge at a jeweler.
- Selling the ring for gold? Check 18K ring melt value or the karat × weight calculator.
* Frequently asked
FAQ
- Q. What is UK W½ in other ring size systems?
- A. UK W½ converts to US 11.5 = UK W½ = EU 66 = Japan 25.
- Q. What is the diameter of UK W½?
- A. Inside diameter 21 mm; inside circumference 65.9 mm.
- Q. How should I measure my finger?
- A. Measure at the end of the day when fingers are warm. The ring must clear the knuckle; if knuckle and base differ, size for the knuckle and consider a comfort-fit band.
- Q. Can every ring be resized to this size?
- A. Most gold and platinum bands can move 1–2 sizes. Tension settings, eternity bands, and some titanium/tungsten rings cannot. See a jeweler before ordering a resize.
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