CalcVitalsBody Surface Area Calculator
Body surface area estimates the area of your skin from height and weight. The Mosteller formula — the square root of height × weight ÷ 3,600 — gives 1.84 m² for a person of 70 kg and 175 cm. Most adults land between 1.6 and 2.0 m².
How it works
Body surface area sounds like a curiosity until you meet it in a hospital, where it quietly runs a great deal of dosing. Many medicines — chemotherapy agents most famously — are prescribed per square metre of body surface, because surface area tracks metabolic capacity and organ size better than weight alone does. Burn specialists use the same figure: treatment plans are built on the percentage of total surface area affected.
Nobody measures skin directly outside a research lab, so clinicians estimate it from height and weight. The Mosteller formula (1987) won adoption by being both accurate and computable at a bedside: the square root of height in centimetres times weight in kilograms, divided by 3,600. The older Du Bois formula (1916), fitted to just nine subjects measured in paper moulds, survives as the cross-check shown beside it — the two rarely differ by more than a percent or two.
For everyday purposes your BSA is most useful as context: it is why a dose, a calorie need or a heat-loss estimate that fits a 1.6 m² person does not transfer unchanged to a 2.1 m² person.
The method
Mosteller (1987): BSA = √(height cm × weight kg ÷ 3,600). Du Bois & Du Bois (1916): BSA = 0.007184 × height^0.725 × weight^0.425. Both return square metres.
Frequently asked questions
What is the average body surface area?
About 1.7 m² for an average adult woman and 1.9 m² for an average adult man, though height and weight move it considerably — the calculator's 1.6–2.0 m² band covers most adults.
Why do drug doses use BSA instead of weight?
Because several organs that clear drugs — kidneys especially — scale more closely with surface area than with weight, so dosing per square metre evens out exposure between small and large patients. Not all drugs use it; many use weight, and some use fixed doses.
Which formula do hospitals use?
Mosteller is the most common in modern practice because it needs only a square root. Du Bois remains the historical reference and is still used in some burn and research settings.