16 Body Surface Area

Surface area (A) is an important feature of the human body. Surface area affects the rate at which heat transfers into or out of the body and the rate at which certain chemicals can be absorbed through the skin. The severity of burn injuries depends on the degree of the burn, but also on the percentage of total body surface area affected^[1]. The areas and surface areas of geometric shapes can be found using various formulas, such as for triangles. The surface area of a convoluted shape such as the human body is difficult to measure, but we can use typical ratios (proportions) to quickly approximate body surface area. For example the palm surface area can be easily measured as and the ratio of palm surface area to body surface area is typically 1/200, which might also be written as 1:200, 0.005, or 0.5%^[2].  The units of area will be length units squared, such as square meters (meters squared or m²). We need to be careful when converting units involving powers (squared, cubed, etc.) and the chain-link method allows us to make sure our units cancel correctly.