Body Surface Area Calculator
Enter weight and height to estimate body surface area in square meters with five published formulas, compared side by side.
All formulas compared
| Formula | Equation (W kg, H cm) | BSA (m²) | BSA (ft²) |
|---|
For information only – not medical advice. Do not use this tool on its own to calculate medication doses; drug dosing must be checked by a qualified healthcare professional.
How to use the Body Surface Area Calculator
- Choose metric or imperial units.
- Enter weight and height.
- Pick a main formula – Mosteller is a common default; Haycock is often used for children.
- Press Calculate BSA to see the result in m² and ft², and compare all formulas in the table.
- Optionally enter a dose per m² to see the total – and always have it checked by a clinician.
Body surface area formulas
Body surface area (BSA) is the total area of the skin, in square meters. It cannot be measured easily, so it is estimated from weight (W, kg) and height (H, cm):
| Formula | Equation | Notes |
|---|---|---|
| Du Bois & Du Bois (1916) | 0.007184 × W0.425 × H0.725 | The classic formula, based on 9 people; still widely used |
| Mosteller (1987) | √(W × H ÷ 3600) | Simple to calculate; standard in many hospitals |
| Haycock (1978) | 0.024265 × W0.5378 × H0.3964 | Validated in infants, children and adults |
| Gehan & George (1970) | 0.0235 × W0.51456 × H0.42246 | Derived from 401 measurements |
| Boyd (1935) | 0.0003207 × H0.3 × W(g)0.7285 − 0.0188 log W(g) | Weight in grams; good for a wide range of body sizes |
Worked example
For an adult weighing 70 kg and 175 cm tall, Mosteller gives √(70 × 175 ÷ 3600) = √3.4028 = 1.845 m². Du Bois gives 0.007184 × 700.425 × 1750.725 = 1.846 m². The formulas usually agree within a few percent for average adults, but differ more for children and people with obesity.
Typical BSA values
| Group | Average BSA |
|---|---|
| Newborn | 0.25 m² |
| Child, 2 years | 0.5 m² |
| Child, 9 years | 1.07 m² |
| Child, 10 years | 1.14 m² |
| Adult woman | about 1.6 – 1.8 m² |
| Adult man | about 1.9 – 2.0 m² |
What BSA is used for
BSA is used to dose some medicines, especially chemotherapy (dose in mg/m²), to index cardiac output (cardiac index = cardiac output ÷ BSA), to normalize kidney function (GFR per 1.73 m²) and to estimate burn areas. Because it is an estimate, clinicians choose a formula, sometimes cap BSA at 2.0 m² for certain drugs, and always confirm doses independently.
Frequently asked questions
What is body surface area?
Body surface area (BSA) is the estimated total surface area of the human body, usually given in square meters. An average adult has a BSA of about 1.7 to 2.0 m².
Which BSA formula is best?
No single formula is best for everyone. Mosteller is simple and widely used in hospitals, Du Bois is the historical standard, and Haycock performs well in children. For average adults they agree within a few percent.
How do you calculate BSA with the Mosteller formula?
Multiply weight in kilograms by height in centimeters, divide by 3,600 and take the square root. For 70 kg and 175 cm: √(70 × 175 ÷ 3600) ≈ 1.84 m².
Why is BSA used for drug dosing?
Metabolic rate, blood volume and kidney function scale better with body surface area than with weight alone, so some drugs – especially chemotherapy – are dosed per square meter.
Can I use this calculator for children?
Yes, the formulas accept small weights and heights. Haycock and Mosteller are commonly used in pediatrics. Medication doses for children must always be confirmed by a pediatric professional.
Is this medical advice?
No. It provides estimates for information only and must not be used alone for treatment or dosing decisions.