Body Surface Area (BSA) Calculator
Calculate BSA using Mosteller, DuBois & DuBois, and Haycock formulas. Compare all three results side by side for drug dosing and clinical assessment.
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Disclaimer: For educational purposes only. Not a substitute for clinical judgment.
About This Tool
What Is Body Surface Area?
Body surface area (BSA) is the measured or calculated surface area of the human body, expressed in square meters (m²). It serves as a better indicator of metabolic mass than body weight alone because it correlates more closely with many physiologic parameters including cardiac output, glomerular filtration rate, and basal metabolic rate. BSA is a critical parameter in clinical medicine, used primarily for chemotherapy dosing, calculation of the cardiac index, and adjustment of certain medication doses.
Mosteller vs. DuBois vs. Haycock Formulas
The three most commonly used BSA formulas are the Mosteller (1987), DuBois & DuBois (1916), and Haycock (1978) equations. The Mosteller formula — BSA = √(height × weight / 3600) — is favored in most clinical settings for its simplicity and comparable accuracy. The DuBois formula — BSA = 0.007184 × height^0.725 × weight^0.425 — was the original equation derived from direct body surface measurements. The Haycock formula — BSA = 0.024265 × height^0.3964 × weight^0.5378 — was developed with a focus on pediatric patients and performs well across all age groups. All three produce very similar results for typical adults, with small differences at extremes of body habitus.
Clinical Context
In oncology, BSA-based dosing has been standard practice since the 1950s, though its scientific basis has been questioned. Some agents demonstrate better efficacy-toxicity profiles with flat dosing or pharmacokinetic-guided dosing (e.g., carboplatin using the Calvert formula with AUC-based dosing). For obese patients, many protocols cap BSA at 2.0 m², though ASCO guidelines recommend using actual body weight for most chemotherapy regimens. BSA is also used to calculate the cardiac index (CI = cardiac output / BSA), with normal values of 2.5–4.0 L/min/m², and to index GFR to a standard BSA of 1.73 m².
🔑 Clinical Pearls
- The Mosteller formula is recommended by most oncology guidelines for its ease of calculation and comparable accuracy.
- The Haycock formula is often preferred in pediatrics, as it was validated across a wider range of body sizes including neonates and children.
- In pediatrics, BSA-based dosing is particularly important as weight-based dosing can lead to significant errors at small body sizes.
- ASCO recommends using actual body weight (not capped BSA) for chemotherapy dosing in obese patients — check your specific protocol.
- GFR is normalized to BSA 1.73 m² — this was the average BSA of 25-year-olds in 1927, not a modern average.
- BSA below 1.0 m² is typical for infants and small children — verify pediatric dosing carefully.
Key References
- Mosteller RD. Simplified calculation of body-surface area. N Engl J Med. 1987;317(17):1098.
- DuBois D, DuBois EF. A formula to estimate the approximate surface area. Arch Intern Med. 1916;17(6):863-871.
- Haycock GB, Schwartz GJ, Wisotsky DH. Geometric method for measuring body surface area. J Pediatr. 1978;93(1):62-66.
- Griggs JJ, et al. ASCO Guideline: Appropriate Chemotherapy Dosing for Obese Adult Patients. J Clin Oncol. 2012;30(13):1553-1561.
Formula last verified: February 2026