a method for determining the percentage of total body surface affected by a burn. The formula is derived from the rule of nines; that is, certain body areas account for 9 per cent each and the total body area is given a value of 99. The remaining 1 per cent is allocated to the perineum. The age of the patient is taken into consideration when applying the Berkow formula. For example, the head of a 1-year-old child is proportionately larger than that of an adult; therefore, the 1-year-old's head would account for 19 per cent of total body surface, while the head of an adult would account for 7 per cent.