Nitrox MOD and EAD Calculator
Maximum operating depth of an enriched-air (nitrox) mix, its equivalent air depth for decompression, and the best mix for a planned depth.
Results
Maximum operating depth (MOD)
33.8
m
Equivalent air depth (EAD)
24.4
m
Oxygen partial pressure at that depth
1.28
bar
Best mix for that depth
35.0
%
Over the limit at that depth?
No
What this tool does
Breathing more oxygen than air shortens decompression, but oxygen becomes toxic under pressure, so each mix has a maximum depth at which its oxygen partial pressure reaches the chosen limit — commonly 1.4 bar for the working part of a dive and 1.6 bar as a contingency maximum. The equivalent air depth is the depth at which air would carry the same nitrogen, which is what lets nitrox divers use air tables. Calculations assume sea water at 10 m per bar; fresh water and altitude change them.
Formula
MOD = (ppO₂ max ÷ FO₂ − 1) × 10 m · EAD = (D + 10) × (1 − FO₂) ÷ 0.79 − 10 (sea water, 10 m per bar)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
fo | Oxygen in the mix | % |
pp | Maximum oxygen partial pressure | bar |
d | Planned depth | m |
MOD | Maximum operating depth (MOD) | m |
EAD | Equivalent air depth (EAD) | m |
PP | Oxygen partial pressure at that depth | bar |
BM | Best mix for that depth | % |
EX | Over the limit at that depth? | — |
Worked example
- Oxygen in the mix32 %
- Maximum oxygen partial pressure1.4 bar
- Planned depth30 m
- Maximum operating depth (MOD)33.8 m
- Equivalent air depth (EAD)24.4 m
- Oxygen partial pressure at that depth1.28 bar
- Best mix for that depth35.0 %
- Over the limit at that depth?No
Limitations
- Planning figures only. Diving with enriched air or planning gas needs proper training and certification, a dive computer and an analysed cylinder; never rely on a web calculator in the water.
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.