Body Surface Area (BSA) Calculator
Calculate body surface area using Du Bois or Mosteller formula.
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Body Surface Area
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About
Body surface area (BSA) estimates the body's external surface and is used to standardize certain drug doses and physiological measurements to body size. Which formula to use: the Mosteller formula [BSA = √(height_cm × weight_kg / 3600)] is the simplest and is the recommended default in many institutions — Cancer Care Ontario, for example, advises using Mosteller only, to cut calculation errors. The Du Bois & Du Bois (1916) formula is the historical and most-cited standard, validated across decades, but it tends to underestimate BSA in obese patients; the Haycock formula is commonly preferred in pediatrics. For most adults Mosteller and Du Bois agree within about 2–3%. Use in: standardizing cytotoxic (chemotherapy) drug doses, which are prescribed per square meter (mg/m²) because clearance tracks BSA better than body weight; cardiac index (CI = cardiac output / BSA); normalizing eGFR to the standard 1.73 m² adult body so kidney function is comparable across body sizes; and as background for burn assessment and fluid resuscitation, which use percent of total body surface area burned rather than the m² value itself. Reference values: average adult BSA is roughly 1.9 m² in men and 1.7 m² in women, and 1.73 m² is the historical 'standard' adult value still used for eGFR. Not the same as BMI: BSA estimates surface area for dosing and physiology, whereas BMI (weight ÷ height²) screens weight relative to height.
Formula
Interpretation
Formula comparison
For most adults these formulas agree within ~2–3%. Average adult BSA is roughly 1.9 m² (men) and 1.7 m² (women); 1.73 m² is the historical standard used for eGFR.
| Formula | Year | Best used for | Note |
|---|---|---|---|
| Mosteller | 1987 | General adult / clinical default | Simplest; recommended as the sole formula by some oncology bodies |
| Du Bois & Du Bois | 1916 | Historical standard; many drug monographs | Tends to underestimate BSA in obese patients |
| Haycock | 1978 | Pediatrics | Validated in infants and children |
Clinical uses of BSA
| Use | How BSA is applied |
|---|---|
| Cytotoxic drug dosing | Doses standardized per square meter (mg/m²); clearance tracks BSA better than weight |
| Cardiac index | CI = cardiac output / BSA; normal ~2.5–4.0 L/min/m², < 2.2 suggests cardiogenic shock |
| eGFR normalization | Reported per 1.73 m² so kidney function is comparable across body sizes |
| Burn assessment | Uses % total body surface area burned (not the m² value) to guide fluid resuscitation |
References
- Mosteller RD. Simplified calculation of body-surface area. N Engl J Med. 1987;317(17):1098.
- Du Bois D, Du Bois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med. 1916;17:863-871.
- Cancer Care Ontario. Body Surface Area Calculation — use the Mosteller equation only (drug dosing safety guidance).
- Griggs JJ, et al. Appropriate Chemotherapy Dosing for Obese Adult Patients With Cancer: ASCO Clinical Practice Guideline. J Clin Oncol. 2012;30(13):1553-1561.
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Disclaimer
Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.