Equivalent air depths, ppO₂ and MOD
How deep a mix can go, how much oxygen you’re breathing at depth, and how “deep” a nitrox dive really is for nitrogen purposes. All in metres.
Want these worked out for your dive — plus your no-stop limit and air consumption? Try the free dive planner.
Open the dive planner →These figures show oxygen limits only. They say nothing about narcosis, decompression obligation, your gas supply, the conditions on the day or your own fitness to dive. Plan every dive with your dive centre and instructor, and analyse every cylinder yourself before you breathe from it.
Maximum operating depth
The deepest you may take each mix before its oxygen partial pressure passes the limit. We always round down— a MOD is a ceiling, and a rounded-up ceiling isn’t one.
| Mix | ppO₂ 1.2 | ppO₂ 1.4working | ppO₂ 1.6 | Certification |
|---|---|---|---|---|
| Air (21%) | 47 m | 56 m | 66 m | None |
| Nitrox EAN32 | 27 m | 33 m | 40 m | Enriched air (nitrox) |
| Nitrox EAN36 | 23 m | 28 m | 34 m | Enriched air (nitrox) |
| Nitrox EAN40 | 20 m | 25 m | 30 m | Enriched air (nitrox) |
1.4 is the working limit taught for the planned part of a dive. 1.6 is a contingency ceiling for trained decompression use — not something to plan a recreational dive around.
Equivalent air depth and ppO₂
Each cell shows the equivalent air depth (the air depth with the same nitrogen loading) and the ppO₂you’d be breathing. Greyed cells are past that mix’s MOD at ppO₂ 1.4— don’t go there.
| Depth | 21%O₂ | 24%O₂ | 28%O₂ | 32%O₂ | 36%O₂ | 40%O₂ |
|---|---|---|---|---|---|---|
| 9 m | 9 m0.40 | 9 m0.46 | 8 m0.54 | 7 m0.61 | 6 m0.69 | 5 m0.76 |
| 12 m | 12 m0.47 | 12 m0.53 | 11 m0.62 | 9 m0.71 | 8 m0.80 | 7 m0.88 |
| 15 m | 15 m0.53 | 15 m0.60 | 13 m0.70 | 12 m0.80 | 11 m0.90 | 9 m1.00 |
| 18 m | 18 m0.59 | 17 m0.68 | 16 m0.79 | 15 m0.90 | 13 m1.01 | 12 m1.12 |
| 21 m | 21 m0.66 | 20 m0.75 | 19 m0.87 | 17 m1.00 | 16 m1.12 | 14 m1.24 |
| 24 m | 24 m0.72 | 23 m0.82 | 21 m0.96 | 20 m1.09 | 18 m1.23 | 16 m1.36 |
| 27 m | 27 m0.78 | 26 m0.89 | 24 m1.04 | 22 m1.19 | 20 m1.34 | — |
| 30 m | 30 m0.84 | 29 m0.96 | 27 m1.12 | 25 m1.28 | — | — |
| 33 m | 33 m0.91 | 32 m1.04 | 30 m1.21 | 28 m1.38 | — | — |
| 36 m | 36 m0.97 | 35 m1.11 | 32 m1.29 | — | — | — |
| 39 m | 39 m1.03 | 38 m1.18 | 35 m1.38 | — | — | — |
| 42 m | 42 m1.10 | 41 m1.25 | — | — | — | — |
| 45 m | 45 m1.16 | 43 m1.32 | — | — | — | — |
| 48 m | 48 m1.22 | 46 m1.40 | — | — | — | — |
Read as: EADin metres, then ppO₂. Air (21%) is its own equivalent air depth, which is why that column reads back the depth you’re at.
The mixes
The standard fill. No nitrox certification needed.
The common “sweet spot” blend — longer bottom time within recreational depths.
Richer again, for shallower profiles where bottom time is the point.
Shallow work and decompression use only.
Technical mixes (trimix and other helium blends) aren’t listed: their limits need more than an oxygen calculation, and a MOD on its own would be a misleading answer. If you’re diving those, you already plan them with your team.
These tables are generated from the standard gas equations rather than reproduced from any agency’s card, so the figures here are the same ones Diving Scanner uses when checking whether a gas suits a dive site’s depth. Always analyse your own cylinder.