Body Surface Area
Mosteller, Du Bois, and Haycock BSA formulas side by side for chemo, cardiac index, and pediatrics.
- Dosing chemotherapy or biologics that are prescribed per m²
- Calculating cardiac index from cardiac output
- Renal clearance normalization (BSA-adjusted GFR)
- Pediatric drug dosing where weight-based dosing under- or over-estimates at extremes
- Mosteller and Du Bois agree closely in adult-sized patients; differences become meaningful at the extremes (very small children, very obese adults).
- For BMI > 35, all surface-area formulas overestimate "metabolically active" mass. For carboplatin and other drugs with strict ceilings, capped BSA (often 2.0 m²) is used instead.
- Haycock is preferred in neonates and infants. Du Bois was derived from a tiny adult sample and underperforms there.
- BSA-indexed values (cardiac index, eGFR/1.73 m²) are a normalization tool, not a measurement — interpret in context.
A 0.05 m² difference between formulas usually doesn't matter, but for narrow-therapeutic-index drugs dosed per m² (carboplatin, methotrexate, doxorubicin) it can shift you a full dose tier. Showing all three formulas side by side makes the disagreement visible rather than hidden behind whichever calculator you happened to grab.
| Formula | BSA |
|---|---|
| Mosteller | 1.82m² |
| Du Bois | 1.81m² |
| Haycock | 1.83m² |
| Mean | 1.82m² |
Which formula to use
- Mosteller — most common in oncology / chemotherapy dosing; simplest to remember.
- Du Bois — historic standard; still used in cardiac index reporting.
- Haycock — preferred for pediatrics and infants where Du Bois underestimates.
Frequently asked
Which BSA formula is most accurate?
For adult patients of average size, Mosteller, Du Bois, and Haycock typically agree within 2–3%. Mosteller is the most widely used in clinical practice because it is simpler and validates well against direct measurement. Haycock outperforms the others in pediatrics, particularly in infants under 10 kg.
What is the Mosteller formula for BSA?
BSA (m²) = √(height in cm × weight in kg ÷ 3600). It was published in NEJM in 1987 as a simplified alternative to Du Bois that is easy to compute mentally and performs comparably in adults.
Why does chemotherapy use BSA instead of weight?
Body surface area correlates better than weight with cardiac output, glomerular filtration, and metabolic rate — the parameters that drive clearance of many cytotoxic drugs. Per-m² dosing is the clinical convention for most chemotherapy regimens, although capped BSA or AUC-based dosing (e.g., carboplatin) is increasingly used to avoid overdosing in obesity.
Should I cap BSA in obese patients?
For some agents — most notably carboplatin (Calvert formula) and several monoclonal antibodies — yes. Many institutional protocols cap BSA at 2.0 m² to avoid systematic overdosing in obese patients, since BSA overestimates metabolically active mass at high BMI. Always check the regimen-specific guidance.