Enter the total depth and the nitrogen fraction for the breathing gas into the calculator (you can choose depth units). The calculator will evaluate the Equivalent Air Depth (EAD). 

Equivalent Air Depth (EAD) Calculator

Enter any 2 values to calculate the missing variable

Enter FN as a fraction (0–1), for example 0.65, or as a percent, for example 65 (the calculator will convert percent to a fraction).

Related Calculators

Equivalent Air Depth Formula

EAD = \frac{(D + 33)\,FN}{0.79} - 33

Variables:

  • EAD is the Equivalent Air Depth (ft)
  • D is the total depth (ft)
  • FN is the fraction of nitrogen (for example, 0.65 for 65% nitrogen)

To calculate Equivalent Air Depth, convert the depth to feet (if needed), add 33, multiply by the ratio of the nitrogen fraction to 0.79 (the approximate nitrogen fraction in air), then subtract 33 from the result. Convert back to your preferred depth unit if needed.

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 / 0.79) – 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 = 0.65 (65%)

Equivalent Air Depth (EAD) = ((130 + 33) × 0.65 / 0.79) − 33 ≈ 101.11 ft