What this calculator does
Get an estimate of your body surface area from just your height and weight. Body surface area (BSA) is the total area of the outside of the body, measured in square meters. It's hard to measure in everyday settings. So it's estimated from height and weight, using formulas built from measurements taken in research studies. Physiologists, scientists who study how the body works, use BSA to compare size-related measurements between people of different builds.
This calculator estimates BSA with four well-known formulas. It shows them side by side, so you can see how closely they agree. For a typical adult, the results usually land within a few hundredths of a square meter of each other. The figures are estimates for general information, not medical advice. Any clinical use of BSA should be decided by a qualified healthcare professional.
Where it's used
Why this math matters outside the classroom:
- Square roots. With Mosteller, a 170 cm, 70 kg adult has a surface area of √(170 × 70 ÷ 3600), which is about 1.82 m².
- Non-integer exponents. DuBois raises weight to the power 0.425 and height to 0.725, a hands-on example of exponents that are not whole numbers.
- Comparing formulas. Students put one height and weight into Mosteller, DuBois, Haycock and Boyd to see how closely four published fits agree.
- Pharmacology classes. Pharmacology courses show students that some reference doses are written per square meter of body surface rather than per kilogram.
- Area and volume. Physiology classes use body surface area to explain why heat loss tracks area while body mass tracks volume.
How to use it
- Choose US or metric units.
- Enter height and weight.
- Pick the formula to feature. Mosteller is the default because it's simple and widely used.
- Read the featured result. Then compare it with the other three formulas in the table.
What the inputs mean
- Formula
- Mosteller (1987) is a simplified formula made to be easy to work out. DuBois & DuBois (1916) is the classic formula, based on a small group of adults. Haycock (1978) was built with data that included infants and children. Boyd (1935) uses weight in grams, with a power that changes slightly with weight.
Formula and method
Mosteller: BSA = √(H × W ÷ 3600) DuBois: BSA = 0.007184 × W^0.425 × H^0.725 Haycock: BSA = 0.024265 × W^0.5378 × H^0.3964 Boyd: BSA = 0.0003207 × H^0.3 × Wg^(0.7285 − 0.0188 × log₁₀ Wg)
H is height in centimeters, W is weight in kilograms, and Wg is weight in grams. BSA comes out in square meters (m²). The ^ sign means "raised to the power of", and log₁₀ is the common logarithm (the power of 10 that gives the number). US inputs are converted exactly: 1 in = 2.54 cm and 1 lb = 0.45359237 kg.
The multipliers and powers in each formula come from real measurements. Each formula's authors chose them to fit the body surface areas they measured in their study group. That's why the formulas give slightly different answers, especially for very small, very tall or very heavy bodies.
Worked example
An adult is 5 ft 10 in tall and weighs 180 lb, using the Mosteller formula.
- Convert: (5 × 12 + 10) × 2.54 = 177.8 cm, and 180 × 0.45359237 = 81.647 kg.
- Multiply: 177.8 × 81.647 = 14,516.8; divide by 3,600 to get 4.0324.
- Take the square root: √4.0324 = 2.0081 m².
- For comparison, DuBois gives 1.996 m², Haycock 2.019 m² and Boyd 2.022 m².
Result: The estimated body surface area is about 2.01 m² by Mosteller.
Understanding the result
Adult BSA commonly falls somewhere around 1.6 to 2.2 m², depending on size. A larger value just reflects a larger body. BSA isn't a measure of health or body fat.
Sometimes the four formulas disagree by more than a few percent. That usually means body proportions outside the range the formulas were built on, such as very high weight or very short stature.
Assumptions and limitations
- Height and weight are accurate and current.
- Each formula's published numbers are used without any changes.
- Results are shown to two decimals; the table shows three.
- All four formulas are fitted to limited study groups, and none is exact for every body shape.
- Accuracy is lower at the extremes of size, including very high body weight.
- The calculator gives a general estimate only. It isn't meant to guide any treatment decision.
Frequently asked questions
Which BSA formula is most accurate?
None is best for everyone. Mosteller is widely used because it's simple and agrees closely with the older formulas for typical adults. Haycock was built with data that included children. If a particular setting calls for a specific formula, that choice belongs to the professional using it.
Why do the formulas give different answers?
Each one was fitted to a different, fairly small group of people, using different measuring methods. So their numbers differ. The gap grows for bodies unlike the ones in the original studies.
Is BSA the same as BMI?
No. BMI divides weight by height squared and is used as a rough weight-for-height check. BSA estimates the physical area of the skin in square meters. They relate to size in different ways and are used for different purposes.
How this calculator is checked
Method: Mosteller (1987) √(H·W/3600); DuBois & DuBois (1916) 0.007184·W^0.425·H^0.725; Haycock et al. (1978) 0.024265·W^0.5378·H^0.3964; Boyd (1935) 0.0003207·H^0.3·Wg^(0.7285 − 0.0188·log₁₀Wg). H cm, W kg, Wg grams. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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