How to Calculate Body Surface Area

Body surface area, BSA, is a measure of the total area of skin on the human body. BSA is used mainly by doctors, pharmacologists, and other clinicians when determining proper dosage of medicines. There are 5 common formulas for approximating the surface area of the human body. Each formula is based on certain assumptions about the overall shape of the human body, each is calculated from weight and height measurements, and each returns an approximate surface area in square meters.

Difficulty:

Moderately Easy

Instructions

Things You'll Need

• calculator with exponential function, x^y

1. First, measure your weight in kilograms (kg) and height in centimeters (cm). If you need to convert from pounds and inches, use 1 lb = .4535 kg, and 1 inch = 2.54 cm. Call the weight in kg "W," and the height in cm "H."

2. Now, calculate your approximate BSA using the Mosteller formula, the most commonly used formula.

   BSA = [W^(0.5)][H^(0.5)]/60 m²

   For example, a 69 kg man who is 178 cm tall would have a BSA of

   [69^(0.5)][178^(0.5)]/60
   = [8.3066][13.3417]/60
   = 1.84 m²

3. Next, use the Dubois formula, another popular estimate of BSA.

   BSA = [W^(0.425)][H^(0.725)]/139.2

   For example, the same man given above would have an approximate body surface area of [6.0466][42.8109]/139.2 = 1.86 m²

4. Two more obscure formulas for calculating the area of skin are from Gehan & George, and Hancock. Respectively they are

   BSA = [W^(0.51456)][H^(0.42246)]/42.5532, and
   BSA = [W^(0.5378)][H^(0.3964)]/41.2116

   These equations are very similar and give values very close to one another.

5. You can also calculate the area of a human body surface with this equation, developed by Boyd. Here, weight "W" is in grams, not kilograms. For conversion, 1000 g = 1 kg. Also, the exponent of W is more complicated than before.

   BSA = [W^(P)][H^(0.3)]/3118.179, where

   P = 0.7285 - 0.0188Log(W).Using the same example of the man with H = 178 cm and W = 69000 g, we have

   P = 0.7285 - (0.0188)(4.83885)
   = .63753 and,

   BSA = [1215.933][4.733]/3118.179 = 1.845 m²

Resources

• Online Body Surface Area Calculator