How body surface area is calculated
Body surface area (BSA) estimates the total external area of the body in square metres. It is widely used in medicine, for example to calculate drug doses and assess burns, because it tracks body size better than weight alone. This calculator uses the Mosteller formula, the most common method.
The formula
Mosteller BSA = the square root of (height in cm x weight in kg / 3600).
Worked example
A person 180 cm tall weighing 80 kg has a BSA of about 2.0 square metres.
Mosteller vs Du Bois: which BSA formula to use
Two formulas dominate. Both take height and weight and return body surface area in square metres (m²):
- Mosteller (simplest, most common for drug dosing): BSA = √((height cm × weight kg) ÷ 3600).
- Du Bois & Du Bois (older clinical standard): BSA = 0.007184 × weight kg0.425 × height cm0.725.
Worked example
A person 170 cm and 70 kg: Mosteller = √((170 × 70) ÷ 3600) = √3.31 = 1.82 m². Du Bois gives a very close 1.81 m². The two agree within a percent or two for typical adults.
The average adult BSA is about 1.7 m² (roughly 1.9 m² for men and 1.6 m² for women). BSA is used mainly to dose chemotherapy and some other drugs, and to index cardiac output.
Frequently asked questions
What is body surface area used for?
Mainly in medicine, to calculate drug doses (especially chemotherapy), assess burn extent, and index measurements to body size.
Which BSA formula is this?
The Mosteller formula, the most widely used because it is simple and accurate: the square root of height times weight divided by 3600.
Which formula is this?
The Mosteller formula, chosen for its simplicity and accuracy. Other formulas (Du Bois, Haycock) give very similar results.
What is a normal BSA?
Most adults fall between about 1.5 and 2.2 m², with 1.7 m² a common average.
Can I use it for drug dosing?
No. This is an educational estimate. Real dosing must be done by a qualified professional.
What is the Mosteller formula for BSA?
BSA (m²) = the square root of (height in cm × weight in kg, divided by 3600). It is the formula most used for medication dosing because it is quick and accurate enough.
What is the average body surface area for an adult?
About 1.7 m² on average, with men near 1.9 m² and women near 1.6 m².
Mosteller or Du Bois: does it matter which I use?
For typical adults the two agree within about 1-2%. Mosteller is simpler and is the default for drug dosing; Du Bois is the older reference standard.