Measure the circumference of the center of your knee when stood with a straight leg.
| Size | Range (cm) | Range (Inches) |
| Small | 29cm - 33cm | 11.4" - 13" |
| Medium | 33cm - 37cm | 13" - 14.6" |
| Large | 37cm - 41cm | 14.6" - 16.2" |
| XL | 41cm - 46cm | 16.2" - 17.8" |
| XXL | 46cm - 51cm | 17.8" - 19.4 |
If you are between sizes it is advisable to go for the larger size.