Enter the PAO2 and the PaO2 into the Calculator. The calculator will evaluate the A/A Ratio. 

A/A Ratio Formula

A/A = PAO2 / PaO2


  • A/A is the A/A Ratio ()
  • PAO2 is the PAO2
  • PaO2 is the PaO2

To calculate A/A Ratio, divide the PAO2 by the PAO2.

How to Calculate A/A Ratio?

The following steps outline how to calculate the A/A Ratio.

  1. First, determine the PAO2. 
  2. Next, determine the PaO2. 
  3. Next, gather the formula from above = A/A = PAO2 – PaO2.
  4. Finally, calculate the A/A Ratio.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

PAO2 = 15

PaO2 = 19