BSA in clinical practice: when weight isn't enough
Body weight scales drug dosing reasonably well for most medications. But for chemotherapy agents, the relationship between body weight and drug distribution is complex enough that body surface area became the standard dosing metric in oncology. The logic: BSA correlates with cardiac output, glomerular filtration rate and hepatic blood flow, all of which affect drug clearance.
Which formula to use
Mosteller (1987) is the most used in modern clinical practice: BSA (m²) = √(height cm × weight kg / 3600). Simple, accurate and widely validated. Use this unless your institution or protocol specifies otherwise. DuBois (1916) is the original formula and remains common in renal dosing references: BSA = 0.007184 × height cm^0.725 × weight kg^0.425. Haycock (1978) is preferred for paediatrics and neonates because it was validated specifically in children. Gehan-George (1970) and Boyd are alternatives used in specific contexts.
The differences between formulas are usually less than 5%, which translates to minor dose differences in practice. What matters most is consistency: use the same formula as the protocol you're following.
BSA in chemotherapy dosing
Most intravenous chemotherapy drugs are dosed in mg/m². A patient with a BSA of 1.8 m² prescribed carboplatin at 200 mg/m² receives 360 mg. Dose capping is common: many protocols cap the dose at a BSA of 2.0 m² regardless of actual BSA, to avoid excessive toxicity in large patients. Always check the specific protocol for capping rules. Pair this with our Max Daily Dose Checker and Creatinine Clearance Calculator (used in Calvert formula for carboplatin dosing).
BSA in paediatric dosing
BSA-based dosing is sometimes used for paediatric medications when mg/kg dosing would result in adult doses being exceeded. In oncology, paediatric chemotherapy protocols almost universally use BSA for dosing. For general paediatric dosing, use our Pediatric Dosage Calculator.