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

In clinical practice, Body Surface Area (BSA) is often preferred over simple body weight because it better reflects the amount of metabolically active tissue that requires energy. One way to approximate this metabolic tissue is by calculating fat‑free mass, which comprises everything in the body except adipose tissue—bones, tendons, internal organs, muscles, blood, nerves, and so on. Since fat does not contribute to metabolic activity, fat‑free mass serves as a practical surrogate for true metabolic mass.

BSA also finds application in a range of medical contexts, for instance in assessing cardiac index—linking heart performance to a person’s size—or most frequently in setting chemotherapy doses. Although many oncologists base chemotherapy regimens on a patient’s BSA, critics point out that this method may be unsuitable for drugs with a narrow therapeutic window, where the margin between an effective dose and a toxic one is slim. Moreover, BSA calculations can become unreliable at extreme heights or weights, where Body Mass Index (BMI) might provide a more accurate estimate. Nevertheless, chemotherapy dosing guided by BSA still tends to be more reproducible than dosing based solely on body weight.

The table below lists several widely used equations for calculating BSA, together with links to the original sources for a deeper look at their derivation. The most common of these is the Du Bois formula, which has demonstrated reliable performance for estimating body fat across both obese and lean individuals, unlike the Body Mass Index. In each formula, BSA is expressed in m², with W denoting weight in kg and H representing height in cm.