Body Surface Area Calculator

Body surface area (BSA) is the total area of your skin, expressed in square metres. It is used throughout medicine — most famously to calculate chemotherapy doses, but also in burn assessment, fluid resuscitation and cardiac output indexing — because many physiological processes scale with surface area more closely than with weight.

Several formulas exist. The Du Bois formula, published in 1916, was derived by directly measuring the skin of a small number of subjects and is still the most widely cited. The Mosteller formula, from 1987, is deliberately simple: the square root of height times weight divided by 3600, giving a result in square metres when height is in centimetres and weight in kilograms. Haycock, from 1978, was built specifically for children, in whom the ratio of surface area to weight changes rapidly as they grow.

The three rarely differ by more than a few percent for adults, which is why most clinical settings simply pick one and stay consistent with it. This calculator shows all three plus their average, so you can see how much the choice matters for your own measurements. For a 175 cm, 70 kg adult, all three land close to 1.85 m².

Unless you work in a clinical setting, BSA is mostly a number you will never need. It is included here for completeness, and because it occasionally appears in fitness contexts — for example when normalising VO2 max, cardiac output or drug doses per square metre of skin. Note that the formulas are estimates built from population averages; they carry no information about body composition, and for people at the extremes of height or weight the prediction error grows.

This calculator returns estimates for general information only. It is not medical advice, diagnosis or treatment, and it cannot replace an assessment by a qualified health professional. Individual results vary, and figures such as calorie needs, body-fat percentage and heart-rate zones are approximations based on population averages rather than measurements of you.