Ring Sizes Around ISO 49
| US | UK | ISO / EU | JP / KR | Diameter (mm) | Circumference (mm) |
| 3.5 | G | 46 | 5 | 14.5 | 45.5 |
| 4 | H | 47 | 7 | 14.9 | 46.8 |
| 4.5 | I | 48 | 8 | 15.3 | 48 |
| 5 | J | 49 | 9 | 15.7 | 49.3 |
| 5.5 | K | 51 | 10 | 16.1 | 50.6 |
| 6 | L | 52 | 12 | 16.5 | 51.9 |
| 6.5 | M | 53 | 13 | 16.9 | 53.1 |
Frequently Asked Questions
Does ISO 49 round up or down in US?
A knuckle wider than the base argues for the larger size; a snug 5 that hides the knuckle can be impossible to remove once fingers swell.
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