Body Surface Area Calculator

Body Surface Area (BSA) represents the estimated exterior surface area of the human body. Unlike body weight or height alone, BSA combines both dimensions to give a measure that correlates with physiological parameters such as basal metabolic rate, drug distribution, and renal function scaling. Clinicians commonly use BSA to adjust medication doses — for example in chemotherapy — and to standardize measurements across patients of different sizes.

Several validated formulas exist to calculate BSA. The Mosteller formula is widely used in clinical practice because of its simplicity and reliable accuracy: BSA (m²) = √((height(cm) × weight(kg)) / 3600). The Du Bois formula is another established method: BSA = 0.007184 × weight(kg)^0.425 × height(cm)^0.725. Both produce comparable results for most adults, while small differences can occur in very short, tall, or unusually heavy individuals.

How to use this calculator

Choose your preferred unit system (imperial or metric), enter your weight and height, then press Calculate. In imperial mode, enter weight in pounds and height in feet and inches; the tool converts values to metric internally before computing the formulas. Results are shown in square meters (m²) and include values from both Mosteller and Du Bois calculations for comparison.

Clinical uses and interpretation

BSA is useful for normalizing physiological measurements and determining drug doses that correlate with a patient’s metabolic mass. For example, many chemotherapy agents are dosed per square meter (mg/m²). BSA also plays a role in assessing the extent of burns (percentage of total body surface area affected) and indexing renal clearance and cardiac output. It is important to remember that BSA is one of several factors clinicians use — age, organ function, clinical status, and laboratory results also guide dosing.

Limitations and cautions

No single formula perfectly describes every individual. Pediatric patients, very obese patients, and those with atypical body proportions may require specialized formulas or clinician judgment. This calculator provides estimates for informational purposes and should not replace professional medical advice. Always consult a healthcare provider for clinical decisions and drug dosing.

Example calculation

For an adult with weight 70 kg and height 175 cm, the Mosteller BSA = √((175 × 70)/3600) ≈ 1.84 m². The Du Bois formula will yield a similar value. Use the calculator above with your measurements to see results tailored to your inputs.