Enter the total depth (ft) and the fraction of nitrogen into the Calculator. The calculator will evaluate the Equivalent Air Depth. 

Equivalent Air Depth Formula

EAD = (D + 33) * FN /.79 - 33


  • EAD is the Equivalent Air Depth (ft)
  • D is the total depth (ft)
  • FN is the fraction of nitrogen

To calculate Equivalent Air Depth, add 33 to the depth, multiply by the reaction of nitrogen over .79, then subtract 33 from the result.

How to Calculate Equivalent Air Depth?

The following steps outline how to calculate the Equivalent Air Depth.

  1. First, determine the total depth (ft). 
  2. Next, determine the fraction of nitrogen. 
  3. Next, gather the formula from above = EAD = (D + 33) * FN /.79 – 33.
  4. Finally, calculate the Equivalent Air Depth.
  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.

total depth (ft) = 130

fraction of nitrogen = 65