What is body surface area (BSA)?

Body surface area is the total surface of your body expressed in square meters. It's used in medicine to scale drug doses (especially chemotherapy), calculate cardiac index, and estimate metabolic rates in ways that correlate better than bodyweight alone.

Which BSA formula should I use?

The Du Bois and Du Bois formula (1916) is the historic standard and still widely used. The Mosteller formula (1987) is simpler and gives nearly identical results. Both are accurate to within about 5% for most adults. We show both so you can compare.

What is a normal BSA?

For average adults: men typically have a BSA around 1.9-2.1 m², and women around 1.6-1.8 m². Children range much lower. Very large or very small individuals can fall outside these ranges — the formula accounts for both height and weight.

Why do doctors use BSA instead of weight?

Many drugs and physiological processes scale more closely with body surface area than with bodyweight. For example, cardiac output per square meter of BSA (the "cardiac index") is remarkably consistent across body sizes, making it a useful way to compare heart function across patients.

Can I use this for chemotherapy dosing?

No. While oncologists use BSA to calculate chemotherapy doses, the actual clinical calculation involves validated software, patient-specific adjustments, and physician oversight. This calculator is educational only — never use it to estimate or modify actual medication doses.

Does BSA change with weight loss or gain?

Yes, but less dramatically than weight itself. BSA scales roughly with the square root of weight times height. Losing 10 kg typically drops BSA by about 0.1-0.15 m² in most adults — meaningful for medication dosing but modest in absolute terms.

Body Surface Area (BSA) Calculator

Calculate body surface area using Du Bois, Mosteller, and Haycock formulas.

Calculator

About Body Surface Area

BSA is a core scaling variable in clinical medicine. Unlike BMI, which is a ratio, BSA is an absolute size measurement — the actual area that would cover your body if you unfolded all your skin. It correlates tightly with metabolic rate, cardiac output, kidney function, and drug clearance.

The Three Formulas

Du Bois (1916): 0.007184 × W^0.425 × H^0.725

Mosteller (1987): √(H × W / 3600)

Haycock (1978): 0.024265 × W^0.5378 × H^0.3964

Du Bois is the classical reference. Mosteller is the most commonly used today because it's easier to compute by hand and agrees with Du Bois to within 5%. Haycock performs best at the extremes — very small children or very large adults.

Where BSA Is Used

Chemotherapy dosing: mg per m² rather than per kg
Cardiac index: cardiac output / BSA, comparing heart function across body sizes
Burn assessment: estimating percentage of skin affected (rule of nines)
Drug clearance: many drugs have pharmacokinetics that scale with BSA
Pediatric dosing adjustments

Medical Disclaimer

This calculator is for educational and reference use only. Never use BSA calculations to modify or calculate medication doses on your own. Clinical dosing requires physician oversight and validated software.

Body Surface Area (BSA) Calculator

About Body Surface Area

The Three Formulas

Where BSA Is Used

Medical Disclaimer

Frequently Asked Questions

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