Body Surface Area (BSA) Calculator
Estimate body surface area in m² from height and weight using the Mosteller, Du Bois and Haycock formulas — the basis of many drug and fluid dosing rules.
How it works
Mosteller: BSA = √(height_cm × weight_kg ÷ 3600) · Du Bois: 0.007184 × W^0.425 × H^0.725 · Haycock: 0.024265 × W^0.5378 × H^0.3964
Body surface area (BSA) scales more closely with metabolic rate, cardiac output and drug clearance than body weight alone, so chemotherapy doses, cardiac indices and burn-fluid formulas are all expressed per m². The Mosteller equation is the modern favourite because it needs only a square root, while Du Bois (1916) and Haycock (validated in children) give very similar answers for typical adults. All three cluster within a few percent, which is why any of them is acceptable clinically.
Worked example
For a 175 cm, 70 kg adult, Mosteller gives √(175 × 70 ÷ 3600) = √3.40 = 1.84 m². Du Bois returns 1.85 m² and Haycock 1.85 m² — agreement to within 0.01 m².
Sources: BSA (Wikipedia)
Frequently asked questions
Which BSA formula should I use?
Mosteller is the default in most clinical settings because it is simple and accurate. Du Bois is the historical standard, and Haycock was validated across a wide range including infants. For an average adult all three agree to within about 2%.
Why is BSA used for drug dosing?
Many drugs — especially chemotherapy agents — clear from the body in proportion to metabolic rate, which tracks surface area better than weight. Dosing per m² reduces both under- and over-dosing across body sizes.
What is a normal BSA?
Average adult BSA is roughly 1.7 m² (about 1.9 m² for men and 1.6 m² for women). It rises with both height and weight.
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Educational estimate using standard formulas and population averages — not medical advice. Talk to a qualified clinician before making decisions about diet, training, or pregnancy.