Ring Sizes Around US 5.5
| US | UK | ISO / EU | JP / KR | Diameter (mm) | Circumference (mm) |
| 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 |
| 7 | N | 54 | 14 | 17.3 | 54.4 |
Frequently Asked Questions
Does US 5.5 round up or down in ISO?
Round toward the knuckle-clearing size; wide or domed bands feel a half size tighter, so a 5.5 in a broad band often wears like a 6.
See a number that looks off? Report an error on this page.