Measure the fullest part of your chest with the tape measure horizontal and parallel to the ground.
| UK Size | Inches (Chest) | CM (Chest) |
| S | 39 | 99 |
| M | 41 | 104 |
| L | 43 | 109 |
| XL | 45 | 114 |
| XXL | 47 | 119 |
| Age | Inches (Height) | CM (Height) |
| 2 yrs | 36 | 92 |
| 3 yrs | 39 | 98 |
| 4 yrs | 41 | 104 |
| 5 yrs | 43 | 110 |
| 6 yrs | 46 | 116 |
| 7 yrs | 48 | 122 |
| 8 yrs | 50 | 128 |