Body Surface Area Calculator
The calculator below computes the total surface area of a human body, referred to as body surface area (BSA). Direct measurement of BSA is difficult, and as such many formulas have been published that estimate BSA. The calculator below provides results for some of the most popular formulas.
Table of average BSAs
BSA is often used in clinical purposes over body weight because it is a more accurate indicator of metabolic mass (the body's need for energy). Metabolic mass can be estimated using fat-free mass, where fat-free mass is all of a person's body mass that does not include fat. This includes bones, tendons, inner organs, muscles, blood, nerves, and more. Since body fat is not metabolically active and fat-free mass excludes body fat, fat-free mass is a reasonable estimate of metabolic mass.
BSA is also used in various other clinical settings, such as determining cardiac index (to relate a person's heart performance to their body size) or most commonly, dosages for chemotherapy (a category of cancer treatment). While dosing for chemotherapy is often determined using a patient's BSA, there exist arguments against the use of BSA to determine medication dosages that have a narrow therapeutic index – the comparison of the amount of a substance necessary to produce a therapeutic effect, to the amount that causes toxicity. If the therapeutic index is too narrow, BSA may not be an accurate enough measure, and there is a risk of causing a toxic rather than therapeutic effect. There is also evidence that BSA becomes less accurate at the extremes of height and weight, and BMI may be a better estimate in such cases. Despite these limitations, the effects of chemotherapy dosages as determined by BSA measurements still remain more consistent than those determined by body weight alone.
Below are some of the most popular formulas for estimating BSA, and links to references for each for further detail on their derivations. The most widely used of these is the Du Bois formula, which has been shown to be effective for estimating body fat in both obese and non-obese patients, unlike body mass index. Where BSA is represented in m2, W is weight in kg, and H is height in cm, the formulas are as follows: