How to use it
- Choose US or metric units.
- Enter height and weight.
- Read the Mosteller BSA and the results of the other formulas.
What BSA is used for
Body surface area is an estimate of the total outer surface of the body. Clinicians use it because many body functions scale better with surface area than with weight alone. Common uses include:
- dosing some medications, especially chemotherapy,
- indexing cardiac output and other measurements (cardiac index),
- estimating kidney function relative to body size,
- burn care and fluid calculations.
The average adult BSA is roughly 1.7–1.9 m², a little higher for men and lower for women.
The four formulas
W = weight in kg, H = height in cm. US inputs are converted automatically.
| Formula | Year | Equation |
|---|---|---|
| Mosteller | 1987 | √(H × W ÷ 3600) |
| DuBois and DuBois | 1916 | 0.007184 × W^0.425 × H^0.725 |
| Haycock | 1978 | 0.024265 × W^0.5378 × H^0.3964 |
| Gehan and George | 1970 | 0.0235 × W^0.51456 × H^0.42246 |
Mosteller is popular because it's simple and gives results close to the others for typical adults. DuBois is the oldest and still widely used; Haycock was developed with data including infants and children.
Worked example
An adult who is 5 ft 9 in (175.3 cm) and 165 lb (74.8 kg):
Mosteller BSA = √(175.3 × 74.8 ÷ 3600) = √3.64 ≈ 1.91 m²
The other three formulas give values within a few hundredths of that. The calculator shows all four, their average and the spread between the highest and lowest.
When formulas disagree
For average adults the formulas agree closely. The differences grow for children, very small or very large people and people with obesity, because the formulas were developed on different groups. That's why it matters which formula a clinic uses, and why dose calculations are always done and checked by the care team.
Important safety note
This tool is for learning and checking, not for dosing medication yourself. Your doctor or pharmacist determines any BSA-based dose and may cap or adjust it. The calculator is informational and isn't medical advice. All calculations happen in your browser; nothing is sent anywhere.
Typical BSA values
| Person | Approximate BSA |
|---|---|
| Newborn | 0.2–0.25 m² |
| 10-year-old child | about 1.1 m² |
| Adult woman | about 1.6–1.8 m² |
| Adult man | about 1.9–2.0 m² |
These are rough figures; the calculator gives the value for your exact height and weight. 1 m² is about 10.8 square feet.
Frequently asked questions
What is a normal body surface area?
For adults, roughly 1.6 to 2.0 m², with an average around 1.7–1.9 m².
Which BSA formula is most commonly used?
Mosteller is very common because it's simple; DuBois and DuBois is also widely used.
How do I calculate BSA with the Mosteller formula?
Multiply height in cm by weight in kg, divide by 3,600, and take the square root.
Can I use pounds and inches?
Yes. Choose US units; the calculator converts them before applying the formulas.
Sources
- Mosteller RD: Simplified calculation of body-surface area. N Engl J Med 1987 (PubMed)
- Du Bois D, Du Bois EF: A formula to estimate the approximate surface area if height and weight be known (1916; reprinted in Nutrition 1989, PubMed)
- Redlarski G, Palkowski A, Krawczuk M: Body surface area formulae: an alarming ambiguity (Sci Rep, 2016)
Last reviewed: November 14, 2026 · Kitpebble editorial team
Change log
- : Sources expanded; FAQ and content reviewed.
For general information only; not medical advice or a diagnosis. How we write and review our pages