Chinese Rule of Nines: Based on actual measurements, the human body is estimated in units of "nine" according to anatomical parts, that is, one "nine" for the head and neck, two "nines" for both upper limbs, three "nines" for the trunk, and five "nines" plus "one" for both lower limbs (including the buttocks). For children, the head area is relatively larger, and the lower limbs are relatively smaller, changing with age. The age factor is added or subtracted accordingly when calculating the area, with 12 years as the age boundary.

The burn area is expressed as a percentage relative to the body surface area. Before the 1960s, China used foreign methods such as Wallace's Rule of Nines. During application, it was found that it did not completely match the body surface area of the Chinese population. In the early 1960s, the body surface area of the Chinese population was measured using the paper casting method. After statistical processing, it was simplified into a formula, creating a classification method suitable for the body surface area of the Chinese population: the Chinese Rule of Nines.