| O'Neill product size (EU) | UK size | USA size | Footwear length closed-toe (cm) | Footwear length sandals (cm) |
| 36 | 3/4 | 5/6 | 23.4 | 24.0 |
| 37 | 4 | 6 | 24.0 | 24.7 |
| 38 | 5 | 7 | 24.7 | 25.4 |
| 39 | 6 | 8 | 25.4 | 26.0 |
| 40 | 7 | 9 | 26.0 | 26.7 |
| 41 | 7/8 | 9/10 | 26.7 | 27.4 |
| 42 | 8 | 10 | 27.4 | 28.0 |
| 43 | 9 | 10 | 28.0 | 28.7 |
| 44 | 10 | 11 | 28.7 | 29.4 |
| 45 | 11 | 12 | 29.4 | 30.0 |
| 46 | 12 | 13 | 30.0 | 30.7 |
| 47 | 13 | 14 | 30.7 | 31.4 |