Follows is a quick reference guide to enable you to easily convert from US to Metric to UK size (and vice versa).
| US Size | Metric (mm) | UK (Imperial) Size |
|---|---|---|
| 0000 | 1.0 | 18 |
| 000 | 1.25 | 17/15 |
| 00 | 1.5 | 15/14 |
| 0 | 2.0 | 14 |
| 1 | 2.25 | 13 |
| 1.5 | 2.5 | --- |
| 2 | 2.75 | 12 |
| 2.5 | 3.0 | --- |
| 3 | 3.25 | 10 |
| 4 | 3.5 | --- |
| 5 | 3.75 | 9 |
| 6 | 4.0 | 8 |
| 7 | 4.5 | 7 |
| 8 | 5.0 | 6 |
| 9 | 5.5 | 5 |
| 10 | 6.0 | 4 |
| 10.5 | 6.5 | 3 |
| 11 | 8.0 | 0 |
| 13 | 9.0 | 00 |
| 15 | 10.0 | 000 |
| 17 | 12.0 | --- |
| 19 | 15.0 | --- |
| 35 | 19.0 | --- |
| 50 | 25.0 | --- |