Body Surface Area (BSA) Calculator
Body Surface Area Calculator
Body surface area (BSA) is a critical measurement in clinical medicine for drug dosing, fluid resuscitation in burns, and normalizing physiological measurements. Unlike weight, BSA accounts for the distribution of tissues across the body, making it a more accurate basis for many medical calculations.
Conversion Formula
Mosteller (1987): BSA = sqrt(height(cm) × weight(kg) / 3600). This simplified version of the DuBois formula requires only weight and height and is accurate for most clinical purposes.
Step-by-Step Examples
170 lbs (77 kg), 70 in (178 cm), imperial = BSA: 1.95 m²
sqrt(178 × 77.1 / 3600) = sqrt(13713.8 / 3600) = sqrt(3.809) = 1.952 m²
60 kg, 165 cm, metric = BSA: 1.66 m²
sqrt(165 × 60 / 3600) = sqrt(9900 / 3600) = sqrt(2.75) = 1.658 m²
Frequently Asked Questions
What is body surface area (BSA)?
Body surface area is the total outer surface of the human body measured in square meters. An average adult has a BSA of approximately 1.7-1.9 m². A 170 lb (77 kg), 5'10" (178 cm) person has a BSA of about 1.93 m² using the Mosteller formula.
Why is BSA used in medicine?
BSA is used instead of weight for dosing chemotherapy drugs, burn treatment area calculations, and cardiac output normalization. It provides a more accurate scaling factor than weight alone because drug distribution across the body correlates better with surface area. For example, a chemotherapy dose might be 100 mg/m², so a patient with BSA 1.9 m² would receive 190 mg.
How accurate is the Mosteller formula?
The Mosteller formula (1987) is widely used in clinical practice due to its simplicity and accuracy. It agrees closely with more complex formulas (DuBois, Gehan-George) within 2-3% for most adult body types. For children and very obese patients, more specialized formulas may be preferred.