How body surface area calculator works
Body surface area (BSA) is the measured or estimated surface of the human body, expressed in square metres (m²). Unlike BMI, which is a ratio of weight to height, BSA estimates an actual area, which is why clinicians use it to scale drug doses (notably chemotherapy), set cardiac output indices and grade burn extent. A typical adult falls between about 1.6 and 1.9 m², children lower and very tall or heavy adults higher.
Because no single formula is universal, this calculator computes four standard ones side by side. Du Bois: BSA = 0.007184 × weight^0.425 × height^0.725 (the 1916 original, still the most cited). Mosteller: BSA = √(height × weight / 3600), the simple square-root method widely used at the bedside. Haycock: BSA = 0.024265 × weight^0.5378 × height^0.3964, popular in paediatrics. Gehan & George: BSA = 0.0235 × height^0.42246 × weight^0.51456, fitted from a large study sample. The headline number is the Du Bois result, and the mean of the four is shown for comparison.
Enter height and weight in centimetres and kilograms, or switch to inches and pounds — the tool converts to metric before applying the formulas, so the result is identical either way. Plausibility guards catch common unit mix-ups such as typing feet into a centimetre field. BSA estimates agree within a few percent for most body sizes, but they can drift for extreme heights or weights, and no calculator replaces the dosing protocol your prescriber or care team uses.