Body surface area calculator
Estimate body surface area from height and weight with the Du Bois formula.
What this calculator covers
Use this calculator when you need a quick body surface area estimate from weight and height without hiding the formula path. The result stays grounded in the Du Bois equation and keeps the converted metric inputs visible.
Surface area estimates can be useful as a rough normalization step, but they are still model outputs rather than direct measurements. If an exact clinical value matters, treat the result as a starting estimate instead of a final instruction.
Frequently asked questions
- What is body surface area used for?
- BSA is commonly used in medical and research contexts to normalize values that scale with body size, such as cardiac output benchmarks or chemotherapy dosing protocols. It captures both height and weight in a single number, which is more representative of body dimensions than weight alone.
- Why does the calculator use the Du Bois formula?
- The Du Bois equation, published in 1916, remains widely cited in clinical reference tables and pharmaceutical literature. More recent formulas exist and may differ slightly, but Du Bois is the baseline most practitioners recognize, making results easier to compare with existing references.
- Does a heavier person always have a larger BSA than a taller person?
- Not necessarily — both dimensions contribute, but they use different exponents (0.425 for weight and 0.725 for height). A tall, lean person can have a larger BSA than a shorter, heavier person, which is why the formula captures size more completely than weight alone.
- Is this result the same as what a clinical measurement would show?
- No. The Du Bois formula is a mathematical model fitted to a small historical dataset, so it is an approximation. Direct skin-surface measurement is impractical in most settings, and research has shown the formula can diverge from measured values in patients at the extremes of height or weight.
Tool
Run the calculation
Result
RESULT · BSA
â„–136
Primary result
1.85 m^2
Using the Du Bois formula, 70.0 kg and 175.0 cm estimate body surface area at 1.85 m^2.
- Metric weight used
- 70.00 kg
- Metric height used
- 175.00 cm
- Estimated BSA
- 1.85 m^2
- Square-foot equivalent
- 19.89 ft^2
Step-by-step solution
- 1.Convert the selected inputs into metric terms for the published equation: 70.00 kg and 175.00 cm.
- 2.Apply Du Bois: 0.007184 x 70.00^0.425 x 175.00^0.725.
- 3.Round the estimate to 1.85 m^2, or 19.89 ft^2.
Walkthrough
Visual walkthrough
Body surface area formulas scale weight and height nonlinearly so dosing or equipment estimates are not based on weight alone.
01
Normalize the body-size inputs
70.00 kg and 175.00 cm
The Du Bois constants are defined for kilograms and centimeters, so imperial entries are converted first.
02
Apply the Du Bois exponents
0.007184 x weight^0.425 x height^0.725
Both body dimensions matter, but neither is treated as a straight linear multiplier.
03
Read the estimated surface area
The final output is most commonly expressed in square meters, with square feet useful as a rough cross-check.
1.85 m^2