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Body Surface Area Calculator

Estimate body surface area (BSA) from height, weight, and sex using Du Bois, Mosteller, Haycock, and other common formulas, in US or metric units.

US Units

ExampleSample values — edit any field to see your result.

Gender

Only the Schlich formula uses sex; the other estimates are the same for men and women.

ft
in
lb

Results update as you type.

Body surface area (Du Bois)

1.85m²

The Du Bois formula is the most widely cited estimate. Compare Mosteller and the others in the table.

Estimated result

Body mass index
22.9kg/m²

BSA by formula

Formulam²ft²in²
Du Bois1.8519.952,873
Mosteller1.8519.912,868
Haycock1.8519.942,871
Gehan & George1.8620.012,882
Boyd1.8619.982,877
Fujimoto1.7919.302,779
Takahira1.8720.112,896
Schlich1.7719.012,738
Body surface area (Du Bois)1.85 m²

This calculator estimates body surface area (BSA) from height and weight using eight common formulas — Du Bois, Mosteller, Haycock, Gehan & George, Boyd, Fujimoto, Takahira, and Schlich — and also reports BMI. Direct measurement of skin area is impractical, so these equations are the everyday clinical shortcuts. Results are estimates for education and fitness context, not a diagnosis or a dosing tool on their own.

Formula

Every formula below uses weight W in kilograms and height H in centimetres and returns BSA in m². US pounds convert with 0.453592 kg/lb (the same factor as calculator.net). Square feet and square inches use the international foot (1 ft = 0.3048 m).

Du Bois

BSA = 0.007184 × W^0.425 × H^0.725

Mosteller

BSA = 0.016667 × W^0.5 × H^0.5

Haycock

BSA = 0.024265 × W^0.5378 × H^0.3964

Gehan and George

BSA = 0.0235 × W^0.51456 × H^0.42246

Boyd

BSA = 0.03330 × W^(0.6157 − 0.0188 × log10(W)) × H^0.3

Fujimoto

BSA = 0.00883 × W^0.444 × H^0.663

Takahira

BSA = 0.007241 × W^0.425 × H^0.725

Schlich

Women: BSA = 0.000975482 × W^0.46 × H^1.08
Men:   BSA = 0.000579479 × W^0.38 × H^1.24

Fujimoto is often printed as 0.008883. This page uses 0.00883 so the numbers match calculator.net's live results. Mosteller is algebraically the familiar sqrt(W × H / 3600) form, written here with their 0.016667 coefficient.

Typical average BSA

ft²m²
Newborn child2.690.25
Two-year-old child5.380.5
Ten-year-old child12.271.14
Adult female17.221.6
Adult male20.451.9

These are population sketches, not targets. Height, weight, and which formula you use all move the number.

Examples

Man, 5 ft 9 in, 155 lb (US default)

Height is 175.26 cm and weight is 155 × 0.453592 kg. Du Bois is 1.85 m² (19.95 ft², 2,873 in²). Mosteller is also 1.85 m²; Haycock 1.85; Gehan & George and Boyd 1.86; Fujimoto 1.79; Takahira 1.87; Schlich 1.77. BMI is 22.9.

Man, 175 cm, 70 kg (metric)

Du Bois is 1.85 m² (19.89 ft²). Mosteller is 1.84 m². The other adult formulas sit between 1.76 m² (Schlich) and 1.86 m² (Takahira). BMI is 22.9.

Newborn, 50 cm, 3.5 kg (or 3,500 g)

Du Bois is 0.21 m² (2.25 ft²), close to the 0.25 m² newborn average in the table. Mosteller is 0.22 m². Metric grams and kilograms give the same result when the weight is equivalent.

Frequently asked questions

What is body surface area (BSA)?
Body surface area is an estimate of the outer surface of the body, usually in square metres. Direct measurement is hard, so height-and-weight formulas are used instead. Clinicians often prefer BSA to body weight as a rough stand-in for metabolic mass when relating heart output or some medication doses to body size.
Which BSA formula should I use?
There is no single best equation. Du Bois (1916) is still the most widely cited. Mosteller (1987) is a simpler square-root form that many oncology teams use for chemotherapy. Haycock, Gehan & George, and Boyd were checked in children as well as adults. Fujimoto and Takahira came from Japanese samples; Schlich is the only one here that uses sex. This page shows all eight so you can see the spread.
Why is BSA used for chemotherapy doses?
Many chemo protocols size the dose to BSA so people of different builds get a more consistent exposure than they would from body weight alone. That is not a reason to self-dose. Drugs with a narrow window between helpful and harmful amounts may need a more precise measure, and BSA can drift at the extremes of height and weight — BMI is sometimes the better screen in those cases. Follow the regimen your clinician prescribed.
Does gender change the result?
Only the Schlich formula uses sex (separate equations for men and women). Du Bois, Mosteller, Haycock, Gehan & George, Boyd, Fujimoto, and Takahira depend only on height and weight. Gender is still collected so Schlich can be compared on the same inputs.
What is a typical BSA?
Rough averages often quoted are about 0.25 m² for a newborn, 0.5 m² at age two, 1.14 m² at age ten, 1.6 m² for an adult woman, and 1.9 m² for an adult man. Individuals vary with height, weight, and the formula you pick.

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