How this calculator works
- Step 1Height and weight170 cm, 70 kgMeasured without shoes or heavy clothes.
- Step 2FormulaMostellerOr Du Bois, Haycock or Gehan–George.
- Step 3Surface area1.82 m²Square metres of skin, estimated.
Body surface area, BSA, is the estimated area of the skin in square metres. Doctors use it to scale some drug doses and to index measurements such as kidney function and heart output.
Nobody measures it directly in practice. Instead, equations fitted to measured bodies estimate it from height and weight.
Worked example: 170 cm and 70 kg by Mosteller
- BSA
√(height cm × weight kg ÷ 3600)
- Height × weight170 × 7011,900
- ÷ 36003.31
- Square root1.82 m²
The same body gives 1.81 m² by Du Bois. For a typical adult the formulas agree within about 0.03 m².
The formulas compared
Du Bois (1916) was fitted on nine people. Haycock and Gehan–George used larger samples that included children. Mosteller simplified the Gehan–George idea into a single square root.
Where they differ
- Infant, 75 cm, 9 kgMosteller: 0.43 m²Du Bois gives 0.42 m².
- Child, 110 cm, 18 kg0.74 m²The four formulas agree closely.
- 165 cm, 100 kg2.14 m²Du Bois gives 2.06 m².
Differences are largest for babies and very heavy adults; that is when the choice of formula matters most.
Other body measures
Body surface area is used mainly in clinical dosing. Everyday body measures answer different questions.
For weight against height, use the BMI calculator. The body fat calculator estimates composition, and the eGFR calculator estimates kidney filtration from a creatinine result.
Common mistakes
Mistake: Entering height in metres.
Instead: Enter centimetres; 1.70 m is 170 cm.
Mistake: Mixing formulas between visits.
Instead: Use the same formula each time so results are comparable.
Mistake: Setting a drug dose from this page.
Instead: Doses must be set and checked by a doctor or pharmacist.
Methodology and sources
A separate script recomputes every formula in high precision and checks Du Bois in both its centimetre and metre forms.
The formula definitions come from the NCI Thesaurus of the US National Cancer Institute, and Mosteller’s 1987 letter in the New England Journal of Medicine. Sources, the review date and the health disclaimer follow.
Read how we test our calculators, or browse more health calculators.