Body Surface Area Calculator guide
Body Surface Area Calculator: Mosteller, Du Bois and More
Use our body surface area calculator to work out BSA in square metres from height and weight with the Mosteller, Du Bois, Haycock, Gehan and George, and Boyd formulas.
By the AllCalculator editorial teamUpdated 16 October 20261 min read
Body surface area (BSA) is the total area of the outside of your body, measured in square metres. It's used in medicine because it reflects your metabolism better than weight alone. Our Body Surface Area Calculator works it out with five formulas.
How to use the calculator (Body Surface Area Calculator)
- Enter your weight.
- Enter your height.
You'll see your BSA using the Mosteller formula, with four others for comparison.
The formulas
All use weight (W) in kg and height (H) in cm.
- Mosteller: √(H × W ÷ 3600). Simple and the most widely used.
- Du Bois: 0.007184 × W^0.425 × H^0.725. The oldest, from 1916.
- Haycock: 0.024265 × W^0.5378 × H^0.3964. Often used for children.
- Gehan and George: 0.0235 × W^0.51456 × H^0.42246.
- Boyd: uses weight in grams, with a varying power of weight.
For most adults, they agree to within a few percent.
What it's used for
- Chemotherapy: many cancer drugs are dosed per square metre.
- Children's medicines: some doses are based on BSA.
- Heart and kidney tests: results like cardiac index and eGFR are adjusted to a standard body surface area of 1.73m².
A worked example
With the calculator's default settings, a person who is 168cm tall and weighs 70kg has a BSA of √(168 × 70 ÷ 3600) = 1.81m².
Frequently asked questions
What's an average body surface area?
About 1.9m² for adult men and 1.6m² for adult women.
Which formula should I use?
Mosteller is recommended by many hospitals because it's simple and accurate. Your care team will tell you which one they use.
Can I work out my own medicine dose with this?
No. Doses must always be set and checked by a qualified clinician.
For lean mass, which is used for some other doses, see our Lean Body Mass Calculator.
Sources and further reading
Links open official and independent websites in a new tab.
This guide is general information to help you understand your options. It isn't financial, tax, legal or building advice and doesn't take your personal circumstances into account. Figures were checked when the guide was last updated and can change, so confirm anything important with GOV.UK, HMRC, a regulated adviser or a qualified tradesperson.