Nitrox MOD Calculator
Work out the deepest you should take a nitrox mix before oxygen toxicity becomes a risk. Enter the oxygen percentage and a maximum ppO2, then read the MOD in metres and feet.
How to calculate nitrox MOD
- Enter the oxygen percentage of your mix, for example 32 for EAN32.
- Choose a maximum ppO2, usually 1.4 ata working or 1.6 ata contingency.
- Read the maximum operating depth in metres and feet, then plan inside it.
Examples
EAN32 at ppO2 1.4
Oxygen 32%, max ppO2 1.4
MOD 33.75 m (111.375 ft)
EAN36 at ppO2 1.4
Oxygen 36%, max ppO2 1.4
MOD 28.89 m (95.33 ft)
Frequently asked questions
What is the maximum operating depth of a nitrox mix?
MOD is the deepest you can breathe a mix before the oxygen partial pressure passes your chosen limit. Using FO2 as oxygen percent over 100, MOD in metres is (maxPpO2 / FO2 minus 1) times 10, and in feet it is times 33.
Should I use 1.4 or 1.6 ata for the ppO2 limit?
Most agencies use 1.4 ata as the working limit for the bulk of a dive and reserve 1.6 ata for short contingency or decompression segments. The right number depends on your training, workload and conditions.
Why is the MOD shallower for richer mixes?
More oxygen means the partial pressure hits your limit at a lower ambient pressure, so the safe depth shrinks. EAN36 has a shallower MOD than EAN32 at the same ppO2.
Does MOD account for narcosis or no-decompression limits?
No. MOD only bounds oxygen exposure. You still plan nitrogen loading, narcosis and gas supply separately, and a deeper MOD never overrides a shallower no-decompression limit.
Is this a substitute for proper training?
No. This is a training and planning aid only. Get certified for nitrox, follow your training and analyse every cylinder yourself, and always defer to your dive computer and tables in the water.
Related tools
Equivalent Air Depth Calculator
Convert a nitrox dive to its equivalent air depth in metres or feet. Enter the oxygen percentage and depth to read the EAD for table and computer planning.
Best Nitrox Mix Calculator
Find the richest nitrox mix for a planned depth in metres or feet. Enter your target depth and ppO2 limit to get the best oxygen percentage for the dive.
Oxygen Partial Pressure Calculator
Calculate the oxygen partial pressure of a dive gas at depth in metres or feet. Enter the oxygen percentage and depth to check the ppO2 against the 1.4 limit.
Scuba Air Consumption Calculator
Work out your surface air consumption rate from a dive. Enter start and end pressure, time and depth to get a SAC rate in psi or bar per minute for planning.