Using a tailor's tape measure the circumference of the head, one inc ( 2,5 cm) above the eyebrows, above the ears to the rear of the skull. If you have thick hair, or a lot of hair, measure over the hair, not under it. Make sure the tape is not stretched. If you are not sure, check it against a metal builders tape.

Match measurement to chart. If between sizes, choose the next larger size.