What Is Body Surface Area (BSA)?
Body Surface Area is the measured or estimated surface area of the human body, defined by the National Cancer Institute Thesaurus as a measure of the two-dimensional extent of the skin. Unlike body weight, BSA provides a more physiologically meaningful reference for drug dosing because many pharmacokinetic parameters, including renal clearance, hepatic blood flow, and cardiac output, correlate more closely with surface area than with mass alone.
The Four BSA Formulas
| Formula | Year | Equation | Best For |
|---|---|---|---|
| Mosteller ✦ | 1987 | √(H × W / 3600) | Most clinical settings, simple, accurate |
| DuBois & DuBois | 1916 | 0.007184 × H⁰·⁷²⁵ × W⁰·⁴²⁵ | Historical reference; widely cited |
| Haycock | 1978 | 0.024265 × H⁰·³³³³ × W⁰·⁴²⁸⁸ | Neonates & children <10 years |
| Gehan-George | 1970 | 0.0235 × H⁰·⁴²²⁴⁶ × W⁰·⁵¹⁴⁵⁶ | Wide weight range, including obese |
H = height in cm; W = weight in kg. ✦ Recommended for most clinical use.
Clinical Applications of BSA
- Chemotherapy dosing: Most cytotoxic agents (e.g. cisplatin, doxorubicin, paclitaxel) are prescribed as mg/m². The dose per m² is multiplied by the patient's BSA to get the total dose.
- Cardiac index: Cardiac output (L/min) is divided by BSA to produce the cardiac index (L/min/m²), normalising for body size. Normal CI = 2.2–4.0 L/min/m².
- eGFR normalisation: GFR is reported normalised to 1.73 m² (the standard reference BSA from DuBois), a convention recognised by the NIDDK that enables comparison across body sizes.
- Paediatric dosing: BSA-based dosing is preferred for certain drugs in children because it better accounts for developmental differences in pharmacokinetics than weight alone.
Normal BSA Reference Values
| Population | Reference BSA |
|---|---|
| Standard adult (DuBois reference) | 1.73 m² |
| Average adult male | ~1.9 m² |
| Average adult female | ~1.6 m² |
| Newborn (3.5 kg, 50 cm) | ~0.21 m² |
| Child aged 2 (12 kg, 85 cm) | ~0.53 m² |
| Child aged 10 (32 kg, 138 cm) | ~1.09 m² |
Frequently Asked Questions
Which BSA formula should I use for chemotherapy dosing?
The Mosteller formula is recommended for most chemotherapy dosing decisions in adults. It is used in most modern oncology clinical trials and is endorsed by pharmacokinetic studies as the most practical and accurate formula. Some older protocols were derived using the DuBois formula, check the specific chemotherapy protocol to determine which formula was used in dose derivation.
Is BSA-based dosing accurate for obese patients?
BSA-based dosing in obese patients is controversial. Using actual body weight in obese patients gives a larger BSA and therefore higher chemotherapy doses, which may increase toxicity risk. Some oncology guidelines recommend capping BSA at 2.0–2.2 m² or using ideal body weight for certain agents. The Gehan-George formula is considered more accurate across a wide weight range than Mosteller for obese individuals. Always consult current oncology guidelines and a clinical pharmacist.
Why is 1.73 m² used as the reference BSA for GFR?
The 1.73 m² reference comes from DuBois & DuBois's 1916 measurement of the BSA of a reference-size adult (70 kg, 170 cm). Reporting GFR as mL/min/1.73 m² normalises kidney function for body size, making values comparable between a small female and a large male. This convention is embedded in all standard creatinine clearance equations including CKD-EPI and MDRD, the same ones behind our Creatinine Clearance Calculator.
Does this calculator work for children and neonates?
Yes, enter the child's weight and height and the calculator will compute BSA using all four formulas. For neonates and children under 10 years, the Haycock formula is most appropriate and is highlighted in the results. For paediatric drug dosing, always verify calculated doses against your local formulary, our Pediatric Dose Calculator, or a paediatric pharmacist.
Related Tools
For body weight classification, see BMI Calculator.
References
- Mosteller RD. "Simplified calculation of body-surface area." NEJM. 1987;317(17):1098.
- DuBois D, DuBois EF. "A formula to estimate the approximate surface area if height and weight be known." Arch Intern Med. 1916;17(6):863-871.
- Haycock GB, et al. "Geometric method for measuring body surface area: a height-weight formula validated in infants, children, and adults." 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.
⚠️ Medical Disclaimer: BSA calculations are reference tools only. All drug doses must be verified against the specific chemotherapy protocol, current product information, and confirmed by an oncology pharmacist before administration.