Body Area Surface Calculator

What Is Body Surface Area?

Body surface area (BSA) estimates the total area of your skin in square meters. It is widely used in medicine for calculating drug dosages, burn treatment plans, fluid resuscitation, and cardiac index measurements. BSA-based dosing is the standard for chemotherapy and many IV medications because it accounts for body size more precisely than weight alone. This calculator estimates your BSA using the Du Bois, Mosteller, and Haycock formulas.

Common BSA Formulas

The Du Bois formula (1916) is the oldest and most referenced: BSA = 0.007184 × height(cm)^0.725 × weight(kg)^0.425. The Mosteller formula is simpler and equally accurate for most adults: BSA = square root of (height(cm) × weight(kg) / 3600). The Haycock formula is preferred for pediatric patients. For an average adult male at 70 kg and 170 cm, BSA is approximately 1.8 m². For an average adult female at 60 kg and 160 cm, BSA is about 1.6 m². The average adult BSA range is 1.5 to 2.2 m².

Clinical Applications

Chemotherapy doses are almost always calculated per m² of BSA to account for differences in drug metabolism across body sizes. A standard dose might be listed as 75 mg/m², meaning a patient with a BSA of 1.9 m² receives 142.5 mg. Burn severity is assessed as a percentage of total BSA – the "rule of nines" divides the body into sections of 9% or 18% each. Cardiac index (cardiac output divided by BSA) uses body surface area to normalize heart function measurements across patients of different sizes.

BSA vs BMI

BMI measures weight relative to height as a health screening tool. BSA measures physical surface area for clinical dosing and treatment calculations. They serve completely different purposes. A high BMI may indicate excess weight, while BSA simply describes how large you are physically. Both use height and weight as inputs but apply them in different formulas with different clinical applications.

Frequently asked questions