🧑 Body Surface Area (BSA)

Written and maintained by the PhDino author · Last reviewed 21 September 2026 · Checked against 1 independent reference calculation · how PhDino checks its numbers

Estimating total body surface area from height and weight using the Mosteller formula.

Body surface area is used as a dosing basis for certain medications — chemotherapy agents most notably — where BSA correlates better with a drug's distribution and clearance through the body than body weight alone does. Since it can't be measured directly without significant effort, it's instead estimated from more easily measured quantities: height and weight.

Several BSA estimation formulas exist (Du Bois, Mosteller, Haycock, and others), developed at different times using different reference populations. The Mosteller formula used here is valued mainly for its simplicity — a single square root of a straightforward product — while remaining reasonably close to the more complex alternatives across most of the adult size range.

Key formula

BSA (m²) = √(height (cm) × weight (kg) ÷ 3600)

Notes & limitations

• Different BSA formulas can give meaningfully different results for the same person, particularly at unusual heights or weights — clinical protocols that dose by BSA typically specify which formula they expect, and switching formulas isn't interchangeable without checking that.
• BSA-based dosing calculations built on top of this estimate inherit whatever error the estimate itself carries — this is an approximation from two measurements, not a direct physical measurement of surface area.