Place a string or fabric tape measure around your head about 3-4 mm (1/8") above your ear, across the middle of your forehead, completely encircling your head. Hold the tape firmly, but not too tightly.
If your measurement is below 58cm (22.8") we recommend a medium. If you measure 58cm (22.5”) or higher, we recommend you buy a large. If you are around 58cm, are unsure of your choice and typically wear medium/large hats, we recommend you buy a large.