Body Surface Area Calculator

Calculate your body surface area (BSA) using multiple medical formulas. Used for medication dosing and medical calculations.

This calculator estimates body surface area — the figure chemotherapy and burn protocols dose by — using four published formulas at once so you can see how closely they agree. The highlighted result is Mosteller, the modern standard: the square root of height times weight divided by 3600, a formula where height and weight pull with perfectly equal force (a ten percent change in either moves the result by the same amount, since both sit inside one square root). The three alternatives weight the inputs differently: DuBois raises height to a 0.725 power against weight's 0.425, making it the height-sensitive formula, while Haycock and Gehan & George invert that emphasis — their weight exponents (0.5378 and 0.5146) exceed their height exponents, so they respond more to a kilogram gained than to a centimeter gained. In practice the four estimates land within a few percent of each other for ordinary adult builds, which is the point of showing them together: large disagreements between formulas are a signal of an unusual height-to-weight ratio. BSA here assumes adult proportions; the formulas were derived from limited historical samples and the tool makes no adjustment for amputation, edema, or extreme obesity, where clinical judgment overrides any formula.