US / Canada to UK / Australia ring sizes.
US / Canada 8½ = UK / Australia Q½ 18.52 mm across · 58.2 mm around
Both scales describe the same physical ring. The table below converts every size in the range, derived from inner circumference rather than copied.
| US / Canada | UK / Australia | Diameter | Circumference |
|---|---|---|---|
| 3 | F½ | 14.05 mm | 44.1 mm |
| 3½ | G½ | 14.46 mm | 45.4 mm |
| 4 | H½ | 14.87 mm | 46.7 mm |
| 4½ | I½ | 15.27 mm | 48.0 mm |
| 5 | J½ | 15.68 mm | 49.3 mm |
| 5½ | K½ | 16.08 mm | 50.5 mm |
| 6 | L½ | 16.49 mm | 51.8 mm |
| 6½ | M½ | 16.89 mm | 53.1 mm |
| 7 | N½ | 17.30 mm | 54.3 mm |
| 7½ | O½ | 17.71 mm | 55.6 mm |
| 8 | P½ | 18.11 mm | 56.9 mm |
| 8½ | Q½ | 18.52 mm | 58.2 mm |
| 9 | R½ | 18.92 mm | 59.5 mm |
| 9½ | S½ | 19.33 mm | 60.7 mm |
| 10 | T½ | 19.74 mm | 62.0 mm |
| 10½ | U½ | 20.14 mm | 63.3 mm |
| 11 | V½ | 20.55 mm | 64.5 mm |
| 11½ | W½ | 20.95 mm | 65.8 mm |
| 12 | X½ | 21.36 mm | 67.1 mm |
| 12½ | Y½ | 21.76 mm | 68.4 mm |
| 13 | outside range | 22.17 mm | 69.7 mm |
| 13½ | outside range | 22.58 mm | 70.9 mm |
Measure in the evening — fingers swell through the day and in heat — and let your jeweller's own chart take precedence over this one. How to measure at home →