Head size naturally differs between female and male infants, and it is age-dependent. The skull is filled with the brain, cerebrospinal fluid and vascular structures. The shape and size of the head is determined by the above components, as well as skull thickness, rate of the fusion of the cranial sutures, and the development of the frontal sinuses. This article aims to outline a best practice assessment of head circumference and discuss abnormalities that could be seen in general practice.