How to Measure Your Hat Size
The circumference of the head determines the size of the hat. If the circumference measurement is 58cm, choose size 58.
The best way to measure the circumference of the head is to use a soft, flexible, non-stretchable measuring tape.
To ensure you measure the circumference of your head correctly, the tape measure needs to be over the middle of your forehead, just above your ears and sit midway at the back of your head. Do not pull the tape too tightly. If you find yourself in-between two sizes go for the bigger one.
If you do not have a flexible tape measure, you can use a non-stretchy piece of string. Wrap it around the head as suggested and mark it to indicate the circumference. Next, lay the string out on a flat surface and use a ruler to measure it.