Equivalent Air Depth (EAD) Nitrox Calculator

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Depth (meters)

Oxygen Fraction O₂ (%)

Results

Equivalent Air Depth

24.43

meters of seawater

Nitrogen Fraction (N₂)	68%

What is Equivalent Air Depth (EAD)?

Equivalent Air Depth (EAD) is a scuba diving concept that tells you the depth at which breathing ordinary air would expose you to the same nitrogen partial pressure as breathing a nitrogen-reduced nitrox mix at your actual depth. Because enriched air nitrox (EANx) contains more oxygen and less nitrogen than air (21% O₂), the nitrogen load is lower — so the EAD is always shallower than your real depth. Divers use the EAD to look up no-decompression limits on standard air tables and to plan safer, longer bottom times.

EAD is the depth at which breathing air gives the same nitrogen partial pressure as the nitrox mix at the actual depth.

How to use this calculator

Enter your actual depth in meters and the oxygen percentage of your nitrox blend (for example 32 for EAN32). The calculator returns the equivalent air depth in meters of seawater along with the nitrogen fraction of your mix. Plan your dive using the air table value that corresponds to the EAD rather than your real depth.

The formula explained

The metric EAD formula is:

$$\text{EAD} = \frac{1 - \dfrac{\text{O}_2\ (\%)}{100}}{0.79} \times \left( \text{Depth (m)} + 10 \right) - 10$$

Here fO₂ is the oxygen fraction (e.g. 0.32), D is the actual depth in meters, 0.79 is the nitrogen fraction of ordinary air, and 10 converts depth to atmospheres of absolute pressure (10 meters of seawater ≈ 1 atm). The term \((1 - f\text{O}_2)\) is the nitrogen fraction of your mix.

The formula scales the nitrogen content of the mix against air's 0.79 fraction over absolute pressure depth.

Worked example

Suppose you dive to 30 m on EAN32 (fO₂ = 0.32). Then $$\text{EAD} = \frac{1 - 0.32}{0.79} \times (30 + 10) - 10 = \frac{0.68}{0.79} \times 40 - 10 = 0.86076 \times 40 - 10 = 34.43 - 10 \approx 24.43\ \text{m}.$$ So you plan as if you were at about 24 m on air.

FAQ

Why is EAD always less than my actual depth? Because nitrox contains less nitrogen than air, the nitrogen exposure is lower, equivalent to a shallower air dive.

Does this work for plain air? Yes — with 21% O₂ the EAD equals your actual depth, confirming the formula.

Is this a substitute for proper training? No. EAD aids planning but does not replace certified nitrox training, dive computers, or oxygen-toxicity (MOD) checks.