To measure your head circumference and find your size, wrap a (tailor’s)
measuring tape around the widest part of your head - over your hair, from your
forehead, above your ears and around the back of your head, then round to the
front again. Don't pull the measuring tape too tightly or your cap will fit too
tight. Measure it two or three times to be accurate. Use the size obtained to
identify the size of the cap in the table below.