According to my calculations, the circumference is 21.5 inches.5 inches, which is a medium-sized hat with a length that is slightly longer than the standard medium-sized hat.Unfortunately, my head is about the size of a peanut, and its circumference ranges from 19 to 20 inches, so this is going to be too big for me to wear. Please keep in mind that it is on the slightly larger side for my...