Body Surface Area Calculator Formula

Understand the math behind the body surface area calculator. Each variable explained with a worked example.

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Formulas Used

Body Surface Area

bsa_m2 = sqrt(weight_kg * height_cm / 3600)

Body Surface Area

bsa_ft2 = sqrt(weight_kg * height_cm / 3600) * 10.764

Variables

VariableDescriptionDefault
weight_lbsBody Weight(lbs)180
height_inchesHeight(inches)70
weight_kgDerived value= weight_lbs * 0.453592calculated
height_cmDerived value= height_inches * 2.54calculated

How It Works

Mosteller Formula for Body Surface Area

BSA (m2) = sqrt(Weight(kg) x Height(cm) / 3600)

Body surface area is used in medicine for:

  • Chemotherapy dosing
  • Drug dosing calculations
  • Burn assessment
  • Cardiac index calculations

    • Average BSA

    The average adult male BSA is approximately 1.9 m2.

    Worked Example

    A 180 lb, 70-inch tall male.

    weight_lbs = 180height_inches = 70
    1. 01Weight = 81.6 kg, Height = 177.8 cm
    2. 02BSA = sqrt(81.6 x 177.8 / 3600)
    3. 03= sqrt(14,508.48 / 3600)
    4. 04= sqrt(4.030) = 2.01 m2

    Frequently Asked Questions

    What is body surface area used for?

    BSA is primarily used in medicine for calculating drug dosages (especially chemotherapy), determining cardiac output, and assessing burn severity.

    How does BSA differ from BMI?

    BMI measures weight relative to height squared and indicates weight status. BSA measures actual skin surface area and is used for physiological calculations.

    What is the Mosteller formula?

    The Mosteller formula (1987) is the simplest and most widely used BSA formula. It uses the square root of the product of weight and height divided by 3600.

    Ready to run the numbers?

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