Ring Sizes Around ISO 63
| US | UK | ISO / EU | JP / KR | Diameter (mm) | Circumference (mm) |
| 9 | R | 60 | 19 | 18.9 | 59.5 |
| 9.5 | S | 61 | 20 | 19.4 | 60.8 |
| 10 | T | 62 | 21 | 19.8 | 62.1 |
| 10.5 | U | 63 | 23 | 20.2 | 63.4 |
| 11 | V | 65 | 24 | 20.6 | 64.6 |
| 11.5 | W | 66 | 25 | 21 | 65.9 |
| 12 | X | 67 | 26 | 21.4 | 67.2 |
Frequently Asked Questions
Does ISO 63 round up or down in UK?
For a band over 6 mm wide, round up here; the extra room offsets the tighter feel of a broad ring and the swelling that builds by evening.
See a number that looks off? Report an error on this page.