Start With a Diamond
| Diameter (mm) | Circumference (mm) | US | UK | French/German | Italian |
|---|---|---|---|---|---|
| 14.8 | 47.44 | 4 | H½ | 47.5 | 7.5 |
| 15.6 | 49.95 | 5 | J½ | 50 | 10 |
| 16.45 | 52.46 | 6 | L½ | 52.5 | 12.5 |
| 17.3 | 54.98 | 7 | N½ | 55 | 15 |
| 18.2 | 57.49 | 8 | P½ | 57.25 | 17.25 |
| 19 | 60 | 9 | R½ | 60 | 20 |
| 19.9 | 62.52 | 10 | T½ | 62.5 | 22.5 |
| 20.7 | 65.03 | 11 | V½ | 65 | 25 |