The normal, or average head circumference of a person varies by age and by gender. For an adult male, average head circumference is 22 inches. For an adult woman, it is 20 inches.
An average baby head circumference is 12 inches for premature babies and 14 inches for an average-sized baby. A toddler's head circumference is approximately 16 inches, while a child or preteen has an average head circumference of 18 inches.
To accurately measure head circumference, a tape measure should be placed across the forehead and held fitted snugly around the head. The full circumference of the head should be measured for an accurate result