What is body surface area?
Body surface area (BSA) is the total area of your skin in square metres. Doctors use it more than weight to dose some medicines — especially chemotherapy — and to standardise measurements such as kidney function and cardiac output.
This calculator shows BSA by seven published formulas. Mosteller is the most commonly used for its simplicity.
How it is calculated
Mosteller: BSA = √(height cm × weight kg ÷ 3600)
DuBois: 0.007184 × kg^0.425 × cm^0.725
Haycock, Gehan-George, Boyd, Fujimoto and Takahira use similar power-law equations with different constants.
Worked example
170 cm and 70 kg
- Mosteller
- 1.82 m²
- DuBois
- 1.81 m²
- Haycock
- 1.83 m²
- Boyd
- 1.83 m²
Typical BSA values
BSA grows with both height and weight, but more slowly than weight alone, which is why it suits scaling doses and physiological measurements between small and large bodies.
- Average adult: about 1.6–1.9 m².
- Newborn: about 0.25 m².
- Formulas usually agree within about 3%.
- In hospitals BSA is also used to assess burns and to index cardiac output and kidney function.
- Dosing must always follow a doctor's or pharmacist's instructions.