How fast does baby's head grow?

A baby's head grows rapidly in the first year of life, typically increasing in circumference by about 1.5 centimeters (0.6 inches) per month during the first six months. By the age of one, a baby's head size can be approximately 46 to 47 centimeters (18 to 18.5 inches) in circumference. This growth is crucial for brain development, as the brain grows significantly during this period. After the first year, head growth slows down considerably.