How this body surface area calculator works
Your body surface area (BSA) is the total external surface of your body, expressed in square metres (m²). Because it depends on both your height and your weight, it scales with overall body size better than weight alone — which is why it is widely used in medicine to standardise measurements such as drug doses and cardiac index.
BSA cannot be measured directly in everyday settings, so it is estimated with validated equations. The most common is the Mosteller formula because it is simple and accurate for most adults: BSA = √(height cm × weight kg ÷ 3600). This tool also shows three other standard formulas side by side so you can compare:
Mosteller — √(cm × kg ÷ 3600). DuBois — 0.007184 × cm0.725 × kg0.425. Haycock — 0.024265 × cm0.3964 × kg0.5378. Gehan-George — 0.0235 × cm0.42246 × kg0.51456. Imperial inputs are converted first (lb × 0.453592, in × 2.54).
Reference note: results are estimates rounded to two decimals. BSA is used clinically — for example to calculate medication doses — but this tool is informational only and must not be used for dosing or other medical decisions. Always consult a qualified health professional.
Frequently asked questions
- What is body surface area?
- Body surface area (BSA) is the total external surface of the human body, expressed in square metres (m²). Because it scales with both height and weight, it is often a better measure of metabolic size than weight alone, and it is widely used in medicine to standardise things like drug dosing and cardiac index.
- How is BSA calculated?
- BSA is estimated from your height and weight with validated equations. The most common is Mosteller, BSA = √(height in cm × weight in kg ÷ 3600). This calculator also shows the DuBois, Haycock and Gehan-George formulas side by side, which usually agree to within a few hundredths of a square metre.
- Which BSA formula is best?
- There is no single best formula for everyone. Mosteller is the most widely used because it is simple and accurate for most adults, which is why it is highlighted here. DuBois is the classic original equation, while Haycock and Gehan-George perform well across a wide range including children. For typical adults the results are very close.
- What is BSA used for?
- Clinically, BSA standardises measurements to body size — most notably to calculate chemotherapy and other drug doses, to index cardiac output as cardiac index, and to estimate glomerular filtration rate and metabolic rate. It gives a more consistent basis for dosing than weight alone across people of very different sizes.
- What is an average BSA?
- For an average adult, BSA is roughly 1.7 m², with most adults between about 1.5 and 2.0 m². Men tend to be slightly higher than women, and values are lower for children and scale up with height and weight. Your own figure depends on your specific measurements, so use the result above rather than the average.
- Should I consult a professional about BSA?
- Yes if it relates to your care. BSA is used clinically, but this calculator is an educational estimate and is not medical advice; it does not provide diagnosis, treatment or dosing. Never use these figures to calculate medication or make health decisions yourself — always consult a qualified doctor, pharmacist or other health professional, who will use validated clinical tools.