Head circumference: measure the circumference of your head using a measuring tape. Wrap it around your head at the point where the hat will sit.

• Small-Medium: 52-57cm
• Medium-Large: 55-60cm
• Large-XL: 28-63cm
• One size: 55-60cm

If you're on the borderline between two sizes, order the smaller size for a tighter fit or the larger size for a looser fit.