The formula
Mosteller: √(height in cm × weight in kg ÷ 3,600)
Where it comes from
Body surface area scales with metabolic rate more closely than body weight does, which is why chemotherapy doses, burn assessments and paediatric medicine are calculated from it. Mosteller's formula, published in 1987, is the one most used because it is simple enough to do on a calculator and agrees closely with the older, more elaborate ones.
How to work it out by hand
- Multiply your height in centimetres by your weight in kilograms
- Divide by 3,600
- Take the square root
- The result is in square metres
What is worth knowing
The three formulas agree within about 5 % across normal builds, which is why the choice between them rarely matters clinically. Where they diverge is at the extremes: in obesity and in very small children the older Du Bois formula, fitted in 1916 to nine subjects, drifts noticeably. The average adult is around 1.7 m², and doses in oncology are typically expressed as milligrams per square metre for exactly this reason. Anything involving an actual dose belongs with a clinician, not a web page.