Body Surface Area Calculator
Estimate body surface area from height and weight.
Results update as you type.
This calculator provides estimates based on population research. Results are not medical advice. Consult a qualified healthcare provider before making health or nutrition decisions.
How it works
Body surface area is the total measured area of the outside of the human body, expressed in square metres, and it is one of the most useful size descriptors in clinical medicine. Rather than height or weight alone, many physiological quantities scale more closely with surface area, which is why a body surface area calculator sits at the heart of chemotherapy dosing, cardiac index measurement and burn assessment. This tool uses the DuBois and DuBois equation, published in 1916, which the two researchers derived by wrapping subjects in moulded paper patterns and measuring the area against height and weight. The formula multiplies a constant by height raised to one power and weight raised to another, capturing how area grows with both stature and mass but not in simple proportion to either. Oncologists rely on a body surface area calculator because many cytotoxic drugs have a narrow safety margin and are dosed per square metre to balance efficacy against toxicity. Cardiologists divide cardiac output by surface area to compare hearts of different body sizes fairly. Because the DuBois formula was built on a small sample, several alternatives exist, but it remains the default in most clinical references. Treat the result as a standard estimate for reference and dosing context, and always defer to your care team for any medical decision it informs.
BSA = 0.007184 × height(cm)^0.725 × weight(kg)^0.425
The DuBois equation raises height and weight to fractional powers because surface area does not grow in direct proportion to either dimension. Weight scales roughly with volume, a cubic quantity, while area is a squared quantity, so the exponents of 0.725 for height and 0.425 for weight reconcile the two. The leading constant, 0.007184, calibrates the result to square metres from centimetres and kilograms.
Source:DuBois & DuBois (1916)
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter weight and height.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Body surface area updates instantly as you type — no button to press.
Frequently asked questions
Why is body surface area used for drug dosing?
Many drugs, especially chemotherapy agents, distribute and clear in proportion to body size, and surface area tracks that better than weight alone. Dosing per square metre helps keep concentrations within a narrow therapeutic window across patients of very different builds. It is not perfect, and some newer protocols use flat or weight-based dosing, but per-BSA dosing remains standard for many cytotoxic and paediatric medications where precision matters most.
Which BSA formula is most accurate?
No single formula is universally best, because each was derived from a limited sample. DuBois and DuBois from 1916 remains the most widely cited and is the clinical default. Mosteller offers a simpler square-root version that is easier to compute by hand and gives very similar results. Haycock and Gehan-George are tuned for children. For most adults the differences between them are small, typically a few percent.
What is a normal body surface area?
For an average adult, body surface area is often quoted as around 1.7 square metres, with most adults falling between roughly 1.5 and 2.0. Men tend to sit higher than women because of greater average height and weight. Children have much smaller values that rise with growth. Because BSA depends on both height and weight, there is no single normal figure, only a typical range.
How does BSA differ from BMI?
Body mass index divides weight by height squared to gauge whether weight is proportionate to height, and it is used to screen for underweight or obesity. Body surface area instead estimates the physical area of the skin and is used for dosing and physiological scaling. BMI is a ratio with no direct physical meaning, whereas BSA is an actual area in square metres. They answer entirely different questions.
Can I calculate BSA in pounds and inches?
The DuBois formula in this tool expects kilograms and centimetres, so convert first: divide pounds by 2.205 for kilograms, and multiply inches by 2.54 for centimetres. Enter those metric values to get a result in square metres. Some versions of the formula are published with imperial constants, but converting your inputs to metric is the simplest way to use this calculator accurately.