Measurement of the circumference of the child’s head at its largest area (above the eyebrows and ears and around the back of the head). During routine check-ups, the distance is measured in centimeters and compared to previous measurements; normal ranges are based on sex and age (weeks, months).

Measurement of the OFC is an important part of the routine well baby care. Through years of collecting measurements, values for normal growth rates of infants and young children's heads have been obtained. These values have been incorporated into standardized graphs for girls and boys from birth to 18 months of age. During the well baby exam a deviation from the expected normal head growth may alert to the physician to a developing problem.

For example a head that is larger than normal or whose size is increasing faster than normal may be an indication of increased intracranial pressure (there are multiple causes for this condition) while an exceptionally small head size or too slow of growth rate may indicate that the brain is not growing properly. Therefore, the OFC becomes a very simple yet effective means for early detection of certain problems involving the brain.

See also: sutures - separated; fontanelles - bulging; fontanelles - excessively large