Question 1

What is body surface area used for?

Accepted Answer

BSA is primarily used in medicine for drug dosing — particularly for chemotherapy agents, where BSA-based dosing reduces the variability in drug exposure between patients of different sizes. It is also used to calculate cardiac index (cardiac output per m² BSA), glomerular filtration rate corrections for kidney function, and burn area assessments.

Question 2

Which BSA formula is most accurate?

Accepted Answer

No single formula is universally superior. The Mosteller formula is the most widely used in clinical practice because it is simple to calculate. The DuBois & DuBois formula is the historical standard but may slightly underestimate BSA in obese individuals. The Haycock formula is considered particularly reliable for both children and adults. This calculator shows all three so you can see the range.

Question 3

What is a normal body surface area for adults?

Accepted Answer

The normal adult BSA range is approximately 1.7–2.0 m². The average BSA for men is approximately 1.9 m² and for women approximately 1.6 m². These values are used as reference points in clinical practice — for example, cardiac output is often normalised to BSA (called cardiac index) with a normal range of 2.5–4.0 L/min/m².

Question 4

How is body surface area different from body weight for drug dosing?

Accepted Answer

Weight-based dosing (mg/kg) assumes that drug distribution and elimination scale linearly with weight. BSA-based dosing accounts for the fact that many physiological processes — including metabolic rate, organ size, and renal clearance — scale more closely with surface area than weight. This is particularly important for cytotoxic drugs where the therapeutic window is narrow.

Question 5

Can I calculate BSA for a child?

Accepted Answer

Yes. The Haycock formula was specifically validated for use in children and is widely used in paediatric oncology. You can use this calculator for any height and weight. Note that drug dosing for children should always be supervised by a qualified healthcare professional, as paediatric dosing involves additional considerations beyond BSA.

Question 6

Why do the three formulas give different values?

Accepted Answer

Each formula was derived from measurements of different populations and uses slightly different mathematical relationships between height, weight, and surface area. The Mosteller formula uses a simple square root relationship, while the DuBois and Haycock formulas use power functions. The differences between formulas are usually small (within 5–10%), which is clinically acceptable for most applications.

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BSA in Medicine

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