Body Surface Area (BSA)

Occasionally, drugs are dosed according to a patient's
Body Surface Area (BSA), the calculated surface of a human body. BSA is often considered a more accurate measure of metabolic mass than body weight, since it's less affected by irregular amounts of fat tissue.

The BSA Formula we will go over here is called :

The Mosteller formula.


BSA(m2) = [ ( inches x Lbs. ) ÷ 3131 ]½

- or -

BSA(m2) =   √  (inches x Lbs.)  ÷ 3131  

Here's an example:

Example from the video:

Dr. Guzman has prescribed a dosage of 500mg/m2 of drug "P" to a 36 month old boy. The boy weights 33 Lbs. and is 33 Inches tall. What will the dosage be?

1) First, let's find out the BSA :

  1.1)   BSA(m2) =   √  (33 inches x 33 Lbs.)  ÷ 3131  

  1.2)   BSA(m2) =   √  (1089)  ÷ 3131  

  1.3)   BSA(m2) =   √  0.3478122  

  1.4)   BSA         =   0.59 m2

2) Next, apply that to the Dosage:


To prepare for a career as a pharmacy technician, or study the PTCB and ExCPT exams, learning to calculate Body Surface Area (BSA) is recommended. The Mosteller formula is not the only one used to calculate BSA. However, it is mathematically the easiest to calculate. Another formula used is the DuBois and DuBois formula. The tutorial above is for educational purposes only. In the workplace, health-care professionals use the dosage formulas set forth in their respective companies policies.

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