| Inside Diameter | US | UK | Germany | France |
| 15.3 mm | 4.5 | I | 48 (15.3) | 48 |
| 15.6 mm | 5 | J | 49 (15.6) | 49.5 |
| 16.2 mm | 5.5 | K | 51 (16.2) | 50.5 |
| 16.6 mm | 6 | L | 52 (16.6) | 52 |
| 16.9 mm | 6.5 | M | 53 (16.9) | 53 |
| 17.2 mm | 7 | N | 54 (17.2) | 54.5 |
| 17.8 mm | 7.5 | O | 56 (17.8) | 55.5 |
| 18.1 mm | 8 | P | 57 (18.1) | 57 |
| 18.5 mm | 8.5 | Q | 58 (18.5) | 58 |
| 19.1 mm | 9 | R | 60 (19.1) | 59.5 |
| 19.4 mm | 9.5 | S | 61 (19.4) | 61 |
| 19.7 mm | 10 | T | 62 (19.7) | 62 |
Ring Size
Inside Diameter US UK Germany France 15.3 mm 4.5 I 48 (15.3) 48 15.6 mm 5 J 49 (15.6) 49.5 16.2 mm 5.5 K 51 (16.2) 50.5 16.6 mm 6 L 52 (16.6) 52 16.9 mm 6.5 M 53 (16.9) 53 17.2 mm 7 N 54 (17.2) 54.5 17.8 mm 7.5 O 56 (17.8) 55.5 18.1 mm 8 P 57 (18.1) 57 18.5 mm 8.5 Q 58 (18.5) 58 19.1 mm 9 R 60 (19.1) 59.5 19.4 mm 9.5 S
