Calculate body surface area (BSA) using multiple validated formulas. BSA is used in clinical medicine for drug dosing, cardiac output, and burn assessment.
Body surface area (BSA) is the total surface area of the human body, measured in square metres (m²). It is calculated from height and weight using formulas such as Mosteller or Du Bois. In medicine, BSA is often used instead of body weight to guide certain calculations, because it better reflects metabolic size. The average adult BSA is about 1.7 m².
| Formula | BSA (m²) |
|---|
Several validated formulas exist. The Mosteller formula is the most widely used in clinical practice because it is simple and accurate.
Different formulas suit different patients. Most give very similar results for average adults; differences appear at the extremes of size and in children.
| Formula | Best For | Notes |
|---|---|---|
| Mosteller | General clinical use — the common default | Simple, accurate, easy to compute |
| Du Bois | Adults; long-established standard | Can under-estimate in obesity |
| Haycock | Infants and children | Validated across a wide size range |
| Boyd | Paediatrics and research | Uses a more complex equation |
| Gehan & George | Research settings | Derived from direct measurements |
BSA and BMI both use height and weight but answer different questions. BMI screens weight status; BSA estimates metabolic body size for clinical calculations.
| Feature | BSA | BMI |
|---|---|---|
| Measures | Body surface area (m²) | Weight relative to height |
| Main use | Clinical calculations, dosing reference | Weight-status screening |
| Typical adult value | ~1.7 m² | 18.5–24.9 (healthy) |
| Used by | Clinicians, researchers | General public, clinicians |
BSA appears in several areas of healthcare because it scales with metabolic size better than weight alone. General examples include:
BSA is used in Australia for chemotherapy dosing, cardiac output calculations, burn wound assessment, and paediatric drug dosing. The Mosteller formula is most commonly used in Australian clinical practice.
Average adult male: ~1.9 m² | Average adult female: ~1.7 m² | Newborn: ~0.25 m²
Body Surface Area (BSA) is the measured or calculated total surface area of the human body, expressed in square metres (m²). It is used primarily in clinical medicine for calculating drug doses — particularly chemotherapy, burn treatment coverage, and paediatric medication dosing — where dose by body weight alone does not adequately account for individual variation in physiology.
| Formula | Equation | Year |
|---|---|---|
| Du Bois and Du Bois | 0.007184 × H^0.725 × W^0.425 | 1916 (most used) |
| Mosteller | √(H × W / 3600) | 1987 (simple, popular) |
| Haycock | 0.024265 × H^0.3964 × W^0.5378 | 1978 (paediatric) |
| Gehan and George | 0.0235 × H^0.42246 × W^0.51456 | 1970 |
| Population | Average BSA |
|---|---|
| Neonate (newborn) | 0.25 m² |
| Child (2 years) | 0.5 m² |
| Child (10 years) | 1.14 m² |
| Adult female (average) | 1.6 m² |
| Adult male (average) | 1.9 m² |
What is body surface area used for in medicine?
BSA is primarily used for calculating chemotherapy doses, where dosing by total body weight can under or over-dose patients of different body compositions. It is also used in burn injury assessment (percentage of BSA burned), paediatric medication dosing, and cardiac output calculations. The standard adult BSA of 1.73 m² is used as a normalisation reference for kidney function (GFR) reporting.
Which BSA formula is most accurate?
No single formula is definitively most accurate across all populations. The Du Bois formula (1916) is the most widely used historically, but the Mosteller formula is gaining popularity for its simplicity and comparable accuracy. The Haycock formula is preferred for paediatric populations. Different hospitals and oncology protocols may specify which formula to use.
What is a normal body surface area for an adult?
Average BSA is approximately 1.7-1.8 m² for women and 1.9-2.0 m² for men of average Australian height and weight. A 170cm, 70kg woman has a BSA of approximately 1.77 m²; a 180cm, 80kg man approximately 2.0 m². BSA varies less than body weight across individuals, making it useful for dose normalisation.
What is a BSA calculator?
A BSA calculator (body surface area calculator) estimates your total body surface area in square metres from your height and weight, using standard formulas like Du Bois or Mosteller. It is widely used in medicine for dosing — enter your details above.
How do I calculate body surface area?
Enter your height and weight into the calculator and it applies formulas such as Mosteller and Du Bois to estimate your BSA in square metres. The Mosteller formula is the simplest: BSA = the square root of (height in cm × weight in kg ÷ 3600).
What is a normal body surface area?
The average adult body surface area is about 1.7 m², with most adults falling roughly between 1.5 and 2.0 m². Men usually have a slightly larger BSA than women, and BSA increases through childhood as height and weight grow. Values outside the typical range simply reflect body size.
What is the Mosteller formula?
The Mosteller formula is a simple, widely used way to estimate BSA: the square root of (height in cm multiplied by weight in kg, divided by 3600). It is popular in clinical settings because it is easy to calculate by hand yet accurate for most people.
Why is body surface area used in medicine?
BSA scales with metabolic size better than body weight alone, so it is used as a reference in several areas of medicine, including some medication calculations, chemotherapy protocols and indexing of organ measurements. It gives a fairer basis than weight for people of very different builds.
Which BSA formula is most accurate?
For average adults, Mosteller and Du Bois give very similar results, and Mosteller is preferred for its simplicity. For infants and children, formulas like Haycock or Boyd are often chosen because they were validated across a wider range of body sizes. Differences are usually small.
Can I use this calculator for medication dosing?
No. This tool is for education and general information only. Medication and chemotherapy dosing involve clinical judgement, verified measurements and professional protocols. Always rely on a qualified healthcare professional for any dosing or treatment decision — never on an online calculator.
Is BSA different for children?
Yes, because children are smaller, their BSA is much lower than an adult’s and changes rapidly as they grow. Paediatric-specific formulas such as Haycock are often used for accuracy in infants and children. BSA is especially useful in paediatrics for scaling calculations to a child’s size.