Wrap the measuring tape around the fullest part of the head. This will be just above the ears and about a half inch above the eyebrows for most people. Then take the measurement at the forehead. Measure it a couple times to get the most accurate measurement.
| General Size | US | FR | IT | AU |
| XS | 34 | 44 | 44 | 34 |
| S | 36 | 46 | 46 | 36 |
| M | 38 | 48 | 48 | 38 |
| L | 40 | 50 | 50 | 40 |
| XL | 42 | 52 | 52 | 42 |