Calculate Body Surface Area using Mosteller, Du Bois, Haycock, Gehan & George, and Boyd formulas — used in chemotherapy dosing, cardiac index, and burn assessment.
A free, real-time Body Surface Area (BSA) calculator that computes results from all five major published formulas — Mosteller, Du Bois, Haycock, Gehan & George, and Boyd — and shows the average alongside reference values for newborns, children, and adult males/females. BSA is widely used in clinical medicine for chemotherapy dose calculations (mg/m²), cardiac index (CO/BSA), GFR normalization (per 1.73 m²), and burn surface area estimation. Educational tool only — clinical dosing must use validated software and physician oversight.
Body Surface Area is the total external area of the human body, expressed in square metres (m²). Because BSA correlates more closely with metabolic rate, cardiac output, and renal clearance than body weight does, it has become the standard scaling factor in many areas of clinical medicine. A typical adult male has a BSA of about 1.9 m², an adult female about 1.6 m², a 9-year-old child around 1.07 m², and a newborn just 0.25 m². BSA cannot be measured directly without elaborate techniques, so clinicians use validated formulas based on height and weight.
The most familiar application is chemotherapy dosing. Cytotoxic drugs such as 5-fluorouracil, doxorubicin, paclitaxel, and cyclophosphamide are prescribed per square metre (e.g. 75 mg/m²). Carboplatin is the notable exception — it uses the Calvert formula based on glomerular filtration rate. In cardiology, Cardiac Index = Cardiac Output ÷ BSA, with a normal range of 2.5-4.0 L/min/m². In burn medicine, percentage Total Body Surface Area (%TBSA) burned drives fluid resuscitation via the Parkland formula. In nephrology, glomerular filtration rate is normalized to a standard BSA of 1.73 m².
For most adult clinical work, Mosteller — √((H × W) / 3600) — is preferred because it is easy to compute and well-validated. Du Bois remains common in legacy nomograms and older trial protocols. For pediatric patients, especially infants and neonates, Haycock and Boyd tend to fit empirical data better. Disagreements between formulas grow at the extremes of body habitus. In severely obese patients many oncology centres cap BSA at 2.0-2.2 m² to avoid overdosing.
BSA correlates with metabolic rate, cardiac output, and blood volume better than body weight alone. It is therefore the standard for dosing many chemotherapy drugs (mg/m²), normalizing cardiac index (L/min/m²) and GFR (per 1.73 m²), and estimating fluid needs in burn patients via the Parkland formula.
Mosteller is the most popular for adult chemotherapy because it is simple and accurate. Du Bois is the historical reference used in older literature. Haycock and Boyd are preferred in pediatrics, especially neonates and infants. Most clinical results agree within 5%, so showing all five and the average gives the most balanced view.
For adults of average build, the five formulas typically agree to within 0.05-0.10 m². Larger discrepancies appear at extremes — very low weights (neonates) or very high BMIs. Du Bois tends to underestimate BSA in obese patients, while Mosteller stays robust. None is perfect because they were derived from small samples (Du Bois used just 9 subjects in 1916).
BSA dosing has limitations in obese patients (where capping doses is common), in patients with significant edema or amputation, in renal/hepatic impairment, and for many newer targeted therapies and biologics that use flat dosing or weight-based dosing instead. Carboplatin uses the Calvert formula (target AUC × [GFR + 25]), not BSA.
No. This tool is strictly for education and reference. Clinical dose calculations must use validated hospital pharmacy software, double-checked by qualified pharmacists and physicians, with patient-specific adjustments for organ function, prior toxicity, and drug-specific dose caps. Never use a web calculator as the source of a real prescription.
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