Body Surface Area (BSA)
Body surface area by the Mosteller and Du Bois formulas.
Body surface area
1.91 m²
Mosteller formula
Du Bois BSA
1.9 m²
Height
175 cm
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How the Body Surface Area (BSA) works
This Body Surface Area (BSA) calculator estimates the total external surface area of the human body in square meters using the Mosteller and Du Bois formulas — two of the most clinically validated methods in medicine. It is primarily used by healthcare professionals, pharmacists, and patients to support accurate drug dosing, chemotherapy planning, and physiological assessments.
Body surface area is a measurement of the total skin surface of a human body, expressed in square meters (m²). Unlike body weight alone, BSA accounts for the three-dimensional geometry of the body, making it a far superior reference for dosing medications that distribute throughout body tissues rather than accumulating in a single compartment. This is why oncologists, nephrologists, and intensivists rely heavily on BSA when prescribing chemotherapy agents, calculating cardiac index, or estimating kidney function through formulas like the Cockcroft-Gault equation.
This calculator implements two widely used formulas. The Mosteller formula (1987) is favored for its simplicity and ease of mental calculation: BSA (m²) = √(Height(cm) × Weight(kg) / 3600). The Du Bois & Du Bois formula (1916), one of the oldest and historically most referenced, uses a power-law approach: BSA (m²) = 0.007184 × Height(cm)^0.725 × Weight(kg)^0.425. Both formulas take only two inputs — height and weight — yet produce results that closely approximate direct measurements of body surface area across a wide range of adult body types.
The two formulas generally agree within 2–5% for average-sized adults but can diverge more noticeably at extreme body weights or heights. The Mosteller formula tends to be preferred in clinical practice today because of its computational simplicity and robust performance in diverse populations, while the Du Bois formula remains a historical gold standard embedded in older drug-dosing references and institutional protocols. When using this calculator for clinical decision-making, it is important to know which formula your institution's dosing references are based on, so you can match the method consistently.
A common mistake when using BSA-based calculations is relying on estimated or recalled height and weight values. Even small inaccuracies — a few centimeters or kilograms — can meaningfully shift the calculated BSA and therefore the derived drug dose, particularly for high-risk medications like cytotoxic chemotherapy agents. Always use freshly measured, calibrated values. Additionally, most chemotherapy protocols cap BSA at 2.0 m² to avoid overdosing in obese patients, so clinical context and institutional guidelines should always accompany any BSA calculation.
Formula
BSA = √(height_cm × weight_kg / 3600) [Mosteller]
Pro tips
- Always use freshly measured height and weight — even a 2 kg or 2 cm difference can alter BSA enough to change a chemotherapy dose by a clinically relevant margin.
- Check which formula your drug reference or hospital protocol specifies (Mosteller vs. Du Bois) before using a BSA result for dosing; mixing formulas across calculations can introduce systematic errors.
- For pediatric patients, note that BSA-based dosing is standard in oncology but many other pediatric drug doses are weight-based; confirm the intended dosing method before applying BSA.
- If a patient's calculated BSA exceeds 2.0 m², consult your institution's capping policy for cytotoxic agents, as most protocols do not simply scale dose linearly above that threshold.
- Use BSA alongside other clinical parameters — such as renal function, liver function, and performance status — since BSA is one input into a broader dosing decision, not a standalone answer.
Key terms
- Body Surface Area (BSA)
- — The total external surface area of the human body, measured in square meters, used as a physiological reference point for drug dosing and clinical assessments.
- Mosteller Formula
- — A simplified 1987 equation for estimating BSA — √(height_cm × weight_kg / 3600) — widely adopted in modern clinical practice for its accuracy and ease of use.
- Du Bois Formula
- — The original 1916 power-law BSA formula (0.007184 × height_cm^0.725 × weight_kg^0.425) historically considered the reference standard and still embedded in many older dosing protocols.
- Chemotherapy Dosing
- — The process of calculating the appropriate dose of cancer-fighting drugs, typically expressed in mg/m² of BSA, to maximize efficacy while minimizing toxicity.
- Cardiac Index
- — Cardiac output normalized to BSA (liters per minute per m²), used to assess heart performance relative to body size in critical care settings.
- BSA Cap
- — An institutional or protocol-based maximum BSA value (commonly 2.0 m²) applied when calculating chemotherapy doses to prevent dangerous overdosing in patients with larger body sizes.
