| Internal Diameter (mm) | US/CAN Ring Size | UK/AUS Ring Size | German Ring Size |
|---|---|---|---|
| 14.1 mm | 3 | F | 14 |
| 14.5 mm | 3.5 | G | 14.5 |
| 14.9 mm | 4 | H 1/2 | 15 |
| 15.3 mm | 4.5 | I 1/2 | 15.25 |
| 15.7 mm | 5 | J 1/2 | 15.75 |
| 16.1 mm | 5.5 | K 1/2 | 16 |
| 16.5 mm | 6 | L 1/2 | 16.5 |
| 16.9 mm | 6.5 | M 1/2 | 16.75 |
| 17.3 mm | 7 | O | 17.25 |
| 17.7 mm | 7.5 | P | 17.75 |
| 18.1 mm | 8 | Q | 18 |
| 18.5 mm | 8.5 | R | 18.5 |
| 19.0 mm | 9 | S | 19 |
| 19.4 mm | 9.5 | T | 19.5 |
| 19.8 mm | 10 | U | 19.75 |
| 20.2 mm | 10.5 | V | 20.25 |
| 20.6 mm | 11 | W | 20.5 |
| 21.0 mm | 11.5 | X | 21 |
| 21.4 mm | 12 | Y | 21.5 |
| 21.8 mm | 12.5 | Z | 22 |
| 22.2 mm | 13 | Z 1 | 22.25 |
| Circumference (mm) | US/CAN Ring Size | UK/AUS Ring Size | German Ring Size |
|---|---|---|---|
| 44.2 | 3 | F | 14 |
| 45.55 | 3.5 | G | 14.5 |
| 46.8 | 4 | H 1/2 | 15 |
| 48.07 | 4.5 | I 1/2 | 15.25 |
| 49.3 | 5 | J 1/2 | 15.75 |
| 50.56 | 5.5 | K 1/2 | 16 |
| 51.9 | 6 | L 1/2 | 16.5 |
| 53.08 | 6.5 | M 1/2 | 16.75 |
| 54.4 | 7 | O | 17.25 |
| 55.6 | 7.5 | P | 17.75 |
| 57.0 | 8 | Q | 18 |
| 58.12 | 8.5 | R | 18.5 |
| 59.5 | 9 | S | 19 |
| 60.94 | 9.5 | T | 19.5 |
| 62.1 | 10 | U | 19.75 |
| 63.45 | 10.5 | V | 20.25 |
| 64.6 | 11 | W | 20.5 |
| 65.97 | 11.5 | X | 21 |
| 67.2 | 12 | Y | 21.5 |
| 68.49 | 12.5 | Z | 22 |
| 69.76 | 13 | Z 1 | 22.25 |