Body Surface Area (BSA) Calculator
The Body Surface Area (BSA) Calculator estimates your total body surface area from height and weight—an index widely used in clinical dosing, burn assessment, and normalizing measures like cardiac output and kidney function. It’s helpful anytime you need a quick, standardized size metric that’s more informative than weight or BMI alone.
This tool lets you turn simple measurements into a precise BSA value and compare common formulas so you can communicate clearly with clinicians, plan medication or nutrition guidance, and track changes over time. The aim is to give you an accurate, shareable number that supports safer dosing decisions and consistent interpretation across visits and records.
DuBois and Mosteller methods side by side. We support metric and US units and show your BSA in square meters (m²) with a quick comparison between formulas.
We compute body surface area in m² with the DuBois and Mosteller formulas. Toggle units and see how close the methods are.
| Method | Formula | BSA (m²) |
|---|---|---|
| Mosteller | √(height_cm × weight_kg ÷ 3600) | 1.818 |
| DuBois | 0.007184 × height_cm^0.725 × weight_kg^0.425 | 1.810 |
BSA results interpretation
We show Mosteller in the primary banner and DuBois as an alternate. The two methods typically differ by less than 2–3% for most adults. Clinical dosing references often quote Mosteller due to its simplicity.
How it works
BSA approximates the body’s external surface using height and weight. We provide two widely used formulas.
Formulas, assumptions, limitations
Mosteller (primary). BSA = √((height_cm × weight_kg)/3600). Simple, fast, and widely adopted.
DuBois (alternate). BSA = 0.007184 × height_cm^0.725 × weight_kg^0.425. Classic but slightly more complex.
Units. We convert inches → cm (×2.54) and pounds → kg (×0.45359237) before calculating.
Precision. We display to 2–3 decimals. Small input rounding can shift BSA by a few thousandths.
Use. BSA informs medication dosing, metabolic estimates, and physiology normalization.
Use cases & examples
170 cm, 70 kg → Mosteller ≈ 1.84 m²; DuBois ≈ 1.83 m².
67 in, 154 lb → Mosteller ≈ 1.84 m²; DuBois ≈ 1.83 m² after conversion.
The absolute difference between methods is commonly <0.05 m². Either method is acceptable unless a protocol specifies one.
BSA FAQs
Which BSA formula should we use?
Most protocols accept either. Mosteller is popular for its simplicity; DuBois is historical and similar in results.
Why square meters?
BSA approximates a surface area, so square meters (m²) are the natural unit.
How sensitive is BSA to height vs weight?
Both matter; short-term changes in weight shift BSA more than tiny height differences in adults.
Can we use feet and inches?
Yes. Select US units; we convert to cm and kg internally.
Is BSA the same as BMI?
No. BMI is weight/height² and classifies size; BSA estimates surface area.
What’s a typical adult BSA?
Roughly 1.6–2.2 m², depending on body size.
Do decimals matter for dosing?
Clinical contexts set rounding rules. When in doubt, follow the specific protocol.
Body Surface Area (BSA): Formulas, Context, and Practical Use
We frame body surface area as a compact way to scale physiologic phenomena across different body sizes. Because surface area rises sublinearly with mass, BSA helps normalize comparisons, support dosing guidance, and anchor metabolic approximations. In practice, we focus on two well-known methods—Mosteller and DuBois—because they’re broadly accepted and produce similar results in typical ranges.
What is BSA?
Body surface area estimates the total area of the human skin envelope. We never measure it directly—doing so would be impractical—so we rely on formulas that regress height and weight to surface area based on historical datasets. These approximations are sufficient for many clinical calculations, from chemotherapy dosing to renal function normalization.
Why two methods?
The DuBois formula is one of the earliest, derived in 1916 from a small but carefully measured sample. The Mosteller formula, proposed in 1987, is an algebraic simplification that closely tracks more complex models but is easier to compute and memorize. In common use, differences are small—generally within a few percent.
Units and conversions
Our calculator expects height in centimeters and weight in kilograms for both methods. When US customary inputs are selected, we convert inches to centimeters (×2.54) and pounds to kilograms (×0.45359237) before any math. Consistent units eliminate silent errors and make comparisons across methods meaningful.
Rounding and display
We present Mosteller and DuBois to two to three decimals. That level balances readability with practical significance: a difference of 0.01 m² is negligible in most contexts. If your protocol requires a specific rounding rule, always follow those instructions.
Method details
Applications
- Medication dosing schemes when protocols reference BSA.
- Scaling physiological rates or clearances for comparative purposes.
- Normalizing metabolic calculations in research summaries.
Limitations
All BSA equations are approximations from specific cohorts. Extreme statures, edema, amputations, or unusual body compositions can weaken their fit. In those cases, clinical judgment and protocol-specific adjustments matter more than the fourth decimal place.
Worked examples
Consider 170 cm and 70 kg. Mosteller returns √(119000/3600) ≈ 1.84 m². DuBois returns 0.007184 × 170^0.725 × 70^0.425 ≈ 1.83 m². This pattern—high agreement with tiny absolute differences—is typical across common adult inputs.
FAQ deep dive
- Should we average methods? Not usually—pick the method your protocol specifies.
- Can we mix units? No—we convert to metric first to avoid inconsistencies.
- Do decimals impact dosing? Only if a protocol sets thresholds around narrow cutoffs.
Takeaways
- Mosteller is simple and widely used.
- DuBois is historic and close in value.
- Differences are small—focus on consistent inputs and method selection.