How to Measure your Head
If you do not know your hat size, carefully measure your head size by placing a soft tape measure around the circumference of your head, wrapping it around your head just above the ears and across your eyebrows.
Do not pull the tape too tightly unless you want your hat to be as tight. Measure yourself 2-3 times just to be as accurate as possible.
Then use the chart to pick the correct size, if you are between sizes, choose the larger size.