Body Surface Area Calculator
Calculate body surface area (BSA) using Mosteller, DuBois, and Haycock formulas. Used for drug dosing and clinical assessment.
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How to use this calculator
Body surface area (BSA) is measured in m² and used in medical dosing for chemotherapy, cardiac output calculations, and burn assessment. Three formulas — Mosteller (simplest, widely used), DuBois (classical reference), and Haycock (accurate for paediatrics) — are calculated and averaged.
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Enter the patient's weight in kilograms.
- 2
Enter the patient's height in centimetres.
- 3
Review BSA results from three validated formulas plus the average — used for drug dosing or clinical reference.
Frequently asked questions
Why is body surface area used for drug dosing instead of body weight?
BSA correlates better than body weight with many physiological parameters including cardiac output, metabolic rate, renal clearance, and drug distribution volume. This makes BSA-based dosing more precise for drugs with narrow therapeutic windows, particularly chemotherapy agents where under-dosing reduces efficacy and overdosing causes serious toxicity.
Which BSA formula is most accurate?
No single formula is definitively most accurate across all populations. The Mosteller formula is the simplest and most widely used in clinical practice. DuBois is the historical standard used in most reference literature. Haycock performs well in paediatric populations. The average of the three formulas provides a reasonable consensus estimate. Many hospitals standardise on one formula for consistency.
What is the normal BSA for an adult?
The normal BSA range for adults is approximately 1.5–2.0 m². The average adult male has a BSA of about 1.9 m²; the average adult female about 1.6 m². Chemotherapy protocols often use 1.73 m² as a standard reference BSA. Paediatric BSA values are proportionally much lower.
Body Surface Area Calculator — Mosteller, DuBois & Haycock Formulas
Why Body Surface Area Matters in Medicine
Body surface area (BSA) is a critical measurement in clinical medicine, particularly in oncology, cardiology, and critical care. Unlike body weight, BSA accounts for the geometry of the body and correlates more closely with metabolic rate, cardiac output, renal function, and drug pharmacokinetics. Chemotherapy agents such as cisplatin, doxorubicin, and fluorouracil are dosed per m² of BSA because their toxicity is linked to whole-body metabolism rather than simple weight. BSA is also used to calculate the cardiac index (cardiac output per m²), normalise kidney function measurements, and assess the extent of burns using the rule of nines.
Comparing the Three BSA Formulas
The Mosteller formula (1987) is the simplest to calculate — just the square root of height times weight divided by 3600 — and is now the most commonly used in clinical practice. The DuBois formula (1916) was derived from surface measurements on only nine subjects and has been the historical reference standard for over a century. The Haycock formula (1978) was specifically developed and validated in paediatric patients and tends to be more accurate in children and small adults. Research comparing these formulas in large populations shows they agree closely in adults of typical size but diverge at extremes of weight. Averaging the three provides a robust consensus estimate.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →