About this tool
The Body Surface Area Calculator is a free, in-browser tool that estimates BSA in square meters from height and weight using four classic formulas at once: Mosteller (√(height × weight ⁄ 3600)), Du Bois (0.007184 × H⁰·⁷²⁵ × W⁰·⁴²⁵), Haycock and Gehan–George. Enter values in metric or imperial units and all four results update live.
BSA is widely used in physiology and medicine — for indexing cardiac output, estimating metabolic mass and, in clinical settings, dosing certain drugs. The formulas typically agree within a few percent for adults; Mosteller is the most common bedside choice for its simplicity, while Haycock and Gehan–George were derived with better coverage of children. All math happens locally in your browser.
This tool is informational only — it is not medical advice, and it must not be used for actual drug-dosing decisions.
Frequently asked questions
Which BSA formula should I use?
Mosteller is the de-facto standard because it is simple and matches the others closely for adults; Du Bois is the historical reference, while Haycock and Gehan–George were fitted on datasets including infants and children, so they behave better at small body sizes.
Why do the four results differ slightly?
Each formula was regressed on a different measured population decades apart, so their coefficients differ; for typical adults the spread is usually under 3–5%, which is within the error of the underlying measurements.
What is a normal BSA?
Average adult BSA is roughly 1.9 m² for men and 1.6 m² for women, but it scales with body size — the value itself is neither "good" nor "bad", it is simply a size metric.
Can I use this for medication dosing?
No. Although BSA underlies some clinical dosing (e.g. chemotherapy), this calculator is informational only and not medical advice — dose calculations must be done and verified by qualified clinicians with validated tools.
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