BCBetter Calculators

Body Surface Area Calculator

Calculate your body surface area (BSA) using the Mosteller formula.

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Enter your values and click Calculate

How It Works

The Mosteller formula is: BSA (m²) = √(height(cm) × weight(kg) ÷ 3600). The denominator 3600 is derived from converting the formula's original expression in centimeters and kilograms into square meters: since 1 m = 100 cm, one square meter = 10,000 cm², and the formula's internal constant of 0.016667 multiplied through yields the simplified ÷ 3600 form. As a worked example: a person 170 cm tall weighing 70 kg has BSA = √(170 × 70 ÷ 3600) = √(11900 ÷ 3600) = √3.3056 ≈ 1.818 m². The formula was proposed by R.D. Mosteller in 1987 and validated against direct measurements across diverse patient populations. It slightly overestimates BSA for obese individuals compared to more complex formulas (such as DuBois or Haycock), but its simplicity and clinical acceptance make it the preferred method in most hospital pharmacies and oncology treatment protocols.

Examples

Average Adult Male
70 kg at 170 cm — a representative average adult male body size.
Result: BSA ≈ 1.819 m².
Average Adult Female
60 kg at 165 cm — a representative average adult female body size.
Result: BSA ≈ 1.658 m².
Larger Adult
90 kg at 185 cm — a taller, heavier adult patient.
Result: BSA ≈ 2.127 m².

Frequently Asked Questions

Why is BSA used instead of body weight for drug dosing?
BSA correlates more reliably with organ function — particularly kidney glomerular filtration rate and liver metabolic capacity — than body weight alone. For drugs with a narrow therapeutic window (such as many chemotherapy agents), dosing by BSA reduces both under-dosing (which may be ineffective) and over-dosing (which can be toxic) compared to weight-based dosing.
What is the normal BSA for an adult?
Average BSA is approximately 1.7–1.9 m² for adult males and 1.6–1.7 m² for adult females, though these figures vary considerably with height and weight. A BSA of 1.73 m² is often used as a standardized reference value in medical literature when a population average is needed.
How accurate is the Mosteller formula?
The Mosteller formula agrees closely with more complex formulas like DuBois-DuBois for most average-weight adults. For obese patients or premature infants, specialized formulas (such as Haycock for neonates) may be preferred. In clinical practice, the Mosteller formula is accepted as sufficiently accurate for standard adult dosing calculations.

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