Equivalent Air Depth (EAD) Calculator
Calculate the equivalent air depth for any nitrox blend (EAN32, EAN36, custom mix) at a given depth.
Plan dives using standard air decompression tables.
Equivalent Air Depth (EAD)
The Equivalent Air Depth is the depth at which breathing standard air would expose a diver to the same partial pressure of nitrogen as breathing nitrox at the actual dive depth. By converting an EAN dive to its EAD, divers can use ordinary air decompression tables and dive planners — gaining the no-decompression-time advantage of nitrox without needing nitrox-specific tables.
Formula (metric, depth in meters)
EAD = ((1 − FO₂) / 0.79) × (depth + 10) − 10
Formula (imperial, depth in feet)
EAD = ((1 − FO₂) / 0.79) × (depth + 33) − 33
Where FO₂ is the fraction of oxygen in the breathing mix (0.32 for EAN32, 0.36 for EAN36, etc.). 0.79 is the fraction of nitrogen (and other inert gas) in standard air.
Worked Example — EAN32 at 30 m
- FO₂ = 0.32 → fraction inert = 0.68
- EAD = (0.68 / 0.79) × (30 + 10) − 10
- EAD = 0.8608 × 40 − 10
- EAD ≈ 24.4 m
So a 30 m EAN32 dive uses the air no-decompression limit for 24 m — a meaningful boost in bottom time.
Common Mixes
| Mix | FO₂ | MOD @ 1.4 PPO₂ | Bottom-Time Boost |
|---|---|---|---|
| Air | 0.21 | 56.6 m | none (baseline) |
| EAN28 | 0.28 | 40 m | small |
| EAN32 | 0.32 | 33.5 m | moderate |
| EAN36 | 0.36 | 28.9 m | strong |
| EAN40 | 0.40 | 25 m | high |
Maximum Operating Depth (MOD)
Always check the MOD before relying on EAD. MOD = ((PPO₂_max / FO₂) − 1) × 10 (metric) where PPO₂_max is typically 1.4 ATA recreational, 1.6 ATA emergency.
EAD only addresses nitrogen exposure — it does not prevent oxygen toxicity.
Limitations
The EAD assumes the same nitrogen tissue uptake at equal nitrogen partial pressures, which is supported by both the US Navy and recreational dive tables. It does not handle multi-gas profiles, decompression dives, or trimix. For technical or staged decompression diving, use trimix-aware planners and specific tables — never EAD alone.