ZOVATOOL

Body Surface Area Calculator

Average BSA
1.921 m²
Du Bois (1916)
1.927 m²
Mosteller (1987)
1.926 m²
Haycock (1978)
1.930 m²
Gehan-George (1970)
1.935 m²
Boyd (1935)
1.932 m²
Fujimoto
1.875 m²
Used for
• Chemotherapy dosing (mg/m²)
• Cardiac index (CO/BSA)
• Renal clearance normalisation (mL/min/1.73m²)
• Burn assessment (% BSA burned)

How to use the BSA Calculator

  1. Enter patient height and weight — metric or imperial.
  2. Choose formula: Mosteller (most common in US oncology), Du Bois (historical reference), Haycock (pediatric-friendly), Boyd, or Gehan-George.
  3. Calculator returns BSA in m² for all 5 formulas side-by-side.
  4. For chemotherapy dosing: use the institution's preferred formula (usually Mosteller).
  5. For obese patients (BMI > 40), consider capped BSA — discussed in the FAQ.
  6. For cardiac index: Cardiac Output (L/min) ÷ BSA = index (L/min/m²), normal 2.5–4.0.
  7. For burn assessment: compare BSA to burned area (Rule of Nines or Lund-Browder).
  8. Verify pediatric values against age-appropriate norms — newborns ~0.25 m².
  9. Export result for chart documentation with formula name recorded.
  10. Always cross-check with a colleague before finalizing chemo doses.
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Body Surface Area: the number that dictates chemotherapy doses worldwide

Body Surface Area (BSA) is one of the most used numbers in medicine and one of the most casually misunderstood. Chemotherapy doses, cardiac index, burn severity, pediatric drug scaling and glomerular filtration rate are all normalized to BSA in m². Getting the formula right, and knowing when it fails, is a first-year rotation skill that saves lives.

The classical formula is Du Bois (1916), derived from just nine patients but astonishingly durable — modern comparison studies still find it within 2–3% of measured BSA for average adults. Mosteller (1987) simplified the math to √(height × weight ÷ 3600), gained massive traction because it fits on a mental math scratch pad, and became the US oncology default. Haycock (1978) works best in pediatrics. Boyd (1935) and Gehan-George (1970) are more accurate at BSA extremes.

In oncology, BSA scales cytotoxic drug doses because drug distribution in body water and fat correlates with surface area better than with weight alone. Typical dosing ranges: doxorubicin 60 mg/m², paclitaxel 175 mg/m², cyclophosphamide 600 mg/m². A dosing error of even 10% for a narrow therapeutic index drug (like methotrexate high-dose) can cause severe toxicity or subtherapeutic treatment.

The obesity problem: traditional BSA formulas overestimate for BMI > 40 because they assume standard body composition. Uncapped BSA in the morbidly obese can produce dangerously high chemo doses. Most institutions cap BSA at 2.0–2.2 m² for such patients, or dose on adjusted body weight. This is a policy decision that varies — always check institutional protocol before overriding.

Beyond oncology, BSA drives cardiac index (Cardiac Output ÷ BSA, normal 2.5–4.0 L/min/m²), burn management (%TBSA burned via Rule of Nines), pediatric fluid replacement (Parkland formula), and drug pharmacokinetics research. Any time a physiological parameter needs comparison across body sizes, BSA is the denominator. Get comfortable with two or three formulas, know which your hospital uses, and always double-check chemo doses independently.