Body Surface Area Calculator

Body surface area (in m²) is used to dose many drugs — most importantly chemotherapy, which is almost always prescribed per m² — and to index physiological measurements such as cardiac index (cardiac output ÷ BSA) and glomerular filtration rate. It is also used in pediatrics and in estimating burn extent. Because it scales with metabolic rate better than weight alone, BSA is preferred over body weight for many of these calculations.

For most patients it barely matters: Mosteller, Du Bois, Haycock, Gehan-George and Boyd agree to about 0.01 m² at an average build. The differences appear at the extremes. Du Bois was derived from only nine subjects and tends to under-read in obese patients; Haycock and Mosteller are generally favoured in infants and children. Mosteller is the bedside default because it is simple and validated. When the choice would change a dose, use the formula your clinical protocol specifies.

Many chemotherapy protocols cap BSA at roughly 2.0 m² (or use an adjusted/capped BSA) for large patients, because dosing strictly per actual BSA can lead to very high absolute doses and greater toxicity without proven benefit. Capping is a real clinical-practice convention that a bare m² printout omits — always check the specific drug protocol for whether and how BSA is capped or adjusted.

Yes. Switch the units toggle to Imperial and enter height in inches and weight in pounds; the calculator converts to centimetres (× 2.54) and kilograms (× 0.453592) before applying the formula, so the m² result is identical to the metric path. For example 71 in and 165 lb (≈ 180.3 cm and 74.8 kg) gives ≈ 1.94 m² by Mosteller.

No. It is a free, private estimate that runs entirely in your browser. BSA drives chemotherapy and drug doses, cardiac index and pediatric calculations, so any clinical use must be independently verified against the patient, the measured height and weight, the chosen formula and the drug protocol. It is an estimate for education and convenience, not medical advice.