Body Surface Area is the outer surface of the skin covering the human body. The notion of human body surface area is commonly used for the dosage of certain specific drugs (such as cytostatics which are used in oncology therapies), to estimate skin lesions, or to evaluate cardiac output performance.
It is used in the calculation of the surface-based body shape index (SBSI), which gives better estimates of the morbidity of obesity than the body mass index (BMI) for subjects over the age of 18.
The height and the weight of a person are the data that allow, by empirical formulas, an evaluation of its body surface. In practice, nomograms are also often used.
The formula used is the Boyd formula, reputed to be the most precise. This formula is also valid for children, but the use of size makes it impractical for small children. Weight-only assessment is also available for pediatrics.