Question: what is average baby head size?
Answer: The average newborn's head measures 13 3/4 in (35 cm) Generally, a newborn's head is about half the baby's body length in cm plus 10 cm. So a baby that is 18 inches long would be 45.7 centimeters (18 x 2.54). His or her head would be about 32.9 cm or a little under 13 inches.