Body Surface Area (BSA) Calculator

Body surface area (BSA) is a better size descriptor than weight alone for several clinical purposes — chemotherapy dosing, indexing cardiac output, burns assessment and paediatric drug sizing. Because BSA cannot be measured directly at the bedside, it is estimated from height and weight using regression formulas fitted to real measurements. This calculator takes height in centimetres (H) and weight in kilograms (W); imperial inputs are converted first (1 in = 2.54 cm, 1 lb = 0.453592 kg) before any formula runs.

It evaluates five published formulas:

• Mosteller (1987) — BSA = √((H × W) / 3600). Simplest and the modern clinical default.
• Du Bois & Du Bois (1916) — BSA = 0.007184 × W^0.425 × H^0.725. The historical reference standard.
• Haycock (1978) — BSA = 0.024265 × W^0.5378 × H^0.3964. Validated infants → adults; preferred for paediatrics.
• Gehan & George (1970) — BSA = 0.0235 × W^0.51456 × H^0.42246. Derived from an oncology cohort.
• Boyd (1935) — BSA = 0.0003207 × H^0.3 × (1000W)^(0.7285 − 0.0188 × log₁₀(1000W)). Earliest weight-and-height formula; included for comparison.

The Mosteller formula is the default because it is the simplest to compute and the one most hospitals adopt; Du Bois and Du Bois (1916) remains the historical reference standard. The tool shows all five together as a built-in cross-check: for typical adults they cluster within a few percent, and the “spread” figure reports how far any single estimate sits from the five-formula mean. A tight spread means the patient is well inside the range where these formulas were validated.

When you enter a drug dose in mg/m², the patient dose is computed as dose = dose-per-m² × BSA, following standard BSA-based dosing (U.S. National Cancer Institute). The tool also indexes cardiac output: cardiac index (CI) = cardiac output ÷ BSA, so a normal CI of 2.5–4.0 L/min/m² corresponds to the cardiac-output range shown. Results are rounded to two decimal places, the clinical convention. This is an educational reference — dosing output is illustrative and must be confirmed against the patient’s protocol before prescribing.

• Mosteller RD. Simplified Calculation of Body-Surface Area. N Engl J Med 1987;317(17):1098.
• Du Bois D, Du Bois EF. A formula to estimate surface area from height and weight. Arch Intern Med 1916;17:863-871.
• Haycock GB, et al. Geometric method for measuring body surface area. J Pediatr 1978;93(1):62-66.
• Gehan EA, George SL. Estimation of human body surface area from height and weight. Cancer Chemother Rep 1970;54(4):225-235.
• U.S. National Cancer Institute — chemotherapy and BSA-based dosing.

The formulas on this page were last cross-checked against their primary publications on 2026-06-13. This is an educational reference, not medical advice.