Measurement system for assessing burn injury to the total body surface area (TBSA). The body is divided into segments as multiples of 9%. Adults: The external genitals are 1%; each arm is 9%; front and back of the trunk and each leg is counted as 18%; and head is 9%. Children and infants: The head is 18% (larger surface area in proportion to the body) and legs 14% each. The rule of nines estimation of total body surface area (TBSA) burned.