The size of the head is measured by the circumference of the head, measured by a soft ruler from between the eyebrows to the back of the head, through the occipital ridge is the size of the head circumference, the normal adult head circumference standard is 53cm or more. The change of head circumference in the developmental stage is about 34cm for newborns, 8cm in the first six months after birth, 3cm in the second six months, 2cm in the second year, 1.5cm in the third to fourth years, 1.5cm in the fourth to ten years, 53cm or more after the age of 18, and almost no change after that.