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Body Surface Area Calculator
Use this free body surface area calculator to find your BSA in square meters from your height and weight. Enter your measurements in feet and inches or centimeters, and pounds or kilograms, and the calculator shows your BSA using the Mosteller, Du Bois, and Haycock formulas side by side.
Height and weight are the only inputs. Your BSA is estimated from these two numbers — no other measurements are needed.
| Mosteller (standard) | 1.95 m² |
| Du Bois | 1.95 m² |
| Haycock | 1.96 m² |
| BSA in square feet | 21.0 ft² |
How it works
Body surface area is the total area of your skin, measured in square meters. Nobody measures it with a tape measure — instead, doctors estimate it from height and weight, because the two are closely linked to skin area. This calculator runs three published formulas on the same inputs so you can see how closely they agree.
The Mosteller formula is the standard in most clinics. It says BSA equals the square root of height in centimeters multiplied by weight in kilograms, divided by 3,600. It is popular because it is simple, it works well for adults and children, and it is easy to check by hand. The Du Bois formula, published in 1916, is the oldest: BSA equals 0.007184 times height in centimeters raised to the power 0.725, times weight in kilograms raised to the power 0.425. The Haycock formula is similar, with different powers, and is often preferred for children and infants: BSA equals 0.024265 times height to the power 0.3964, times weight to the power 0.5378.
Your height and weight are converted to centimeters and kilograms first if you enter them in feet, inches, or pounds: one inch is 2.54 centimeters, and one pound is 0.453592 kilograms. The calculator then applies all three formulas and shows each result. For most adults the three answers sit within about 0.02 m² of each other, which is why hospitals are happy to use the simplest one, Mosteller, as the standard. The result is also shown in square feet — multiply square meters by 10.764 to convert.
BSA matters because many body processes scale with surface area rather than weight. Cardiac output, kidney filtration, and heat loss all track BSA more closely than weight alone. That is why some medicine doses, especially chemotherapy drugs, are prescribed per square meter of BSA, and why kidney function results are often reported per 1.73 m², the BSA of an average adult. A larger person has a larger BSA, so the same dose per square meter gives them a larger total dose.
Worked example
A man is 5 feet 10 inches tall and weighs 170 pounds.
Step 1: Convert to metric. Height is 70 inches × 2.54 = 177.8 cm. Weight is 170 × 0.453592 = 77.11 kg.
Step 2: Mosteller. Multiply 177.8 × 77.11 = 13,710, then divide by 3,600 = 3.808, then take the square root: 1.95 m².
Step 3: Du Bois. 0.007184 × 177.8^0.725 × 77.11^0.425 = 1.95 m².
Step 4: Haycock. 0.024265 × 177.8^0.3964 × 77.11^0.5378 = 1.96 m².
The tool shows the same result: Mosteller 1.95 m², Du Bois 1.95 m², and Haycock 1.96 m² — about 21.0 square feet. All three formulas agree closely, and 1.95 m² is a typical value for an adult man of this size.
FAQ
What is body surface area (BSA)?
Body surface area is the total surface area of your skin, measured in square meters (m²). It is estimated from your height and weight with a formula, because measuring the skin directly is not practical. Doctors use BSA to size some medicine doses, compare kidney function, and estimate fluid needs.
Which BSA formula is the standard one?
The Mosteller formula is the standard in most hospitals and clinics because it is simple and accurate enough for everyday use: BSA equals the square root of height in centimeters times weight in kilograms divided by 3,600. Du Bois is the oldest formula, from 1916, and Haycock is often preferred for children. For most adults the three formulas agree within a few hundredths of a square meter.
What is a normal body surface area?
For an average adult man, BSA is about 1.9 m², and for an average adult woman it is about 1.6 to 1.7 m². Children have much smaller values — a newborn is around 0.25 m² and a 10-year-old is around 1.1 m². There is no single ideal number: BSA simply reflects your height and weight, so taller and heavier people have a larger BSA.
Why do doctors use BSA instead of weight alone?
Many processes in the body, such as how fast the heart pumps blood and how quickly the kidneys filter it, scale more closely with surface area than with weight alone. Two people can weigh the same but have different heights, and their BSA will differ. Using BSA gives a fairer comparison between people of different builds, which is why drug doses for chemotherapy and some other medicines are often based on it.
Is this body surface area calculator accurate?
The calculator applies the published Mosteller, Du Bois, and Haycock formulas exactly, so the arithmetic is accurate. The formulas themselves are estimates: they predict BSA from height and weight, and the true value measured by body scanning can differ by a few percent. For medical dosing, a clinician should confirm the result.