Gas Management

Equivalent Air Depth Calculator

Find the air depth with the same nitrogen loading as a Nitrox dive, with the formula, PPO₂ at depth, and MOD shown together.

Mix and depth

Enter the analyzed oxygen percentage of a Nitrox mix and the planned seawater depth.

Oxygen

Actual depth

Equivalent air depth: 24.4 m
PPO₂ at this depth: 1.28 ATA
MOD at 1.4 ATA: 33.7 m

Sea-level seawater approximation (10 m per atmosphere) with 79% inert gas in air. The result is unrounded; on a table, round up to the next deeper row.

EAD formula

\text{EAD} \approx (d + 10) \times \frac{\text{FN}_2}{0.79} - 10

Where

$d$: actual depth in meters of seawater
$\text{FN}_2$: nitrogen fraction of the mix (0.68 for EAN32), not a percentage
$0.79$: inert-gas fraction of air used by air tables

Worked example: EAN32 at 30 m gives (30 + 10) × 0.68 ÷ 0.79 − 10 ≈ 24.4 m.

EAD only compares nitrogen loading. It says nothing about oxygen exposure, narcosis, or gas supply. The equivalent air depth guide explains the model and its limits.

Result

EAD 24.4 m

EAN32at 30 m loads nitrogen like air at 24.4 m.

Frequently Asked Questions

What is the equivalent air depth formula?

In meters of seawater, EAD = (depth + 10) × FN2 ÷ 0.79 − 10. In feet of seawater, EAD = (depth + 33) × FN2 ÷ 0.79 − 33. FN2 is the nitrogen fraction of the mix as a decimal (0.68 for EAN32), and 0.79 is the inert-gas fraction of air that air tables assume.

What is the equivalent air depth of EAN32 at 30 meters?

About 24.4 meters: (30 + 10) × 0.68 ÷ 0.79 − 10. In imperial units, EAN32 at 99 feet has an EAD of about 80.6 feet. To use either value with an air table, round up to the next deeper table row.

Does a shallower EAD let me dive deeper on Nitrox?

No. EAD only compares nitrogen loading for decompression purposes. The depth limit on Nitrox comes from oxygen partial pressure, so check the maximum operating depth for the analyzed mix first.

Why can the EAD formula give a negative depth?

A rich mix at a shallow depth can carry less nitrogen pressure than air does at the surface. The equation then returns a negative number, which is not a usable table depth.

Related Guides

Nitrox & oxygen

Equivalent Air Depth (EAD) Explained

Work out the air depth a Nitrox dive is decompression-equivalent to, and see why EAD never changes your oxygen limit.

Nitrox & oxygen

Understanding MOD: Maximum Operating Depth Explained

Learn what Maximum Operating Depth means, how MOD is calculated from oxygen percentage and PPO2 limits, and how to apply it in real dive planning.

Nitrox & oxygen

What is Nitrox? A Complete Guide for Divers

Learn what Nitrox is, how enriched air works, its benefits and risks, and why divers choose it.

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