average head size for a newborn
Increased head circumference. Increased head circumference is when the measured distance around the widest part of the skull is larger than expected for the child's age and background. A newborn's head is usually about 2 cm (centimeters) larger than the chest size. Between 6 months and 2 years, both measurements are about equal. After 2 years, the chest size becomes larger than the head.