Equivalent Air Depth (EAD) Calculator

EAD is the depth at which ordinary air would give the same nitrogen partial pressure as your nitrox mix does at the real depth. Since air tables track nitrogen loading, matching that pressure lets you reuse an air no-decompression table for a nitrox dive.

With FN2 as one minus oxygen percent over 100, EAD in metres is (FN2 / 0.79) times (depth plus 10) minus 10. In feet it is (FN2 / 0.79) times (depth plus 33) minus 33. The 0.79 is the nitrogen fraction of air, and 10 m or 33 ft is the depth of one atmosphere of water.

A nitrox mix holds less nitrogen than air, so at any given depth it loads your body with less nitrogen. The equivalent air depth is therefore shallower than where you actually are, which is exactly why nitrox stretches your no-decompression limit.

Narcosis tracks nitrogen partial pressure, so a lower EAD does suggest less nitrogen narcosis than breathing air at the same depth. Oxygen can be narcotic too at higher pressures, so nitrox is not narcosis free and should not be treated that way.

It computes only the unit you selected. Choose Metres and it returns metres; choose Feet and it returns feet. It does not convert one to the other, because the surface offset differs, 10 m versus 33 ft.

Any value greater than 0 and up to 100. At 21 percent the EAD equals your real depth because the mix is air. Above 21 percent it is shallower, and the depth you type must be greater than zero.

No. EAD is about nitrogen loading and narcosis, not oxygen toxicity. Your maximum operating depth is set by the oxygen partial pressure limit of the mix and is a separate calculation you must also run before diving.

No. The arithmetic runs entirely in your browser, so the oxygen percentage and depth you enter are never sent to a server or stored.

No. This is a training and planning aid only. Get certified for nitrox, analyse every cylinder yourself, follow your training and always defer to your dive computer and tables underwater.