Body Surface Area Calculator
Free body surface area (BSA) calculator — Mosteller, Du Bois, and Haycock formulas in m² from height and weight.
Everyday Uses
Dose scaling
Understand how BSA is used to scale medication and fluid needs.
Clinical study
A quick reference for students learning BSA formulas.
Compare methods
See Mosteller, Du Bois, and Haycock side by side.
Body metrics
Pair with BMI for a fuller picture of body size.
Frequently Asked Questions
What is body surface area (BSA)?
Body surface area is the total surface area of the human body, expressed in square metres. It is widely used in medicine to scale drug doses (especially chemotherapy), fluid needs, and cardiac output, because BSA tracks metabolic mass better than weight alone. The average adult BSA is about 1.7 m².
How do you calculate BSA?
The most common formula is Mosteller's: BSA (m²) = √(height in cm × weight in kg ÷ 3600). For a 175 cm, 70 kg adult that is √(175 × 70 ÷ 3600) ≈ 1.84 m². This calculator also shows the Du Bois and Haycock formulas, which give very similar results.
Which BSA formula should I use?
Mosteller is the most widely used because it is simple and accurate across ages. Du Bois is the classic older formula, and Haycock works well for infants and children. The three usually agree within a few percent; clinical protocols specify which to use. This tool is for general information, not medical dosing.