⚠️ Educational tool — not dive-planning software
This page is for learning and rough estimates only. Always follow your training, your dive tables, and your dive computer — they account for factors a web page cannot. Never plan a real dive from a website.
Common recreational mixes: EAN32 and EAN36. Air is 21%.
Working limit — ppO₂ 1.4
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The conservative limit most agencies teach for the working part of the dive.
Contingency limit — ppO₂ 1.6
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A ceiling for brief contingencies only — not a depth to plan for.
Enter an oxygen percentage between 21 and 100.
How it's calculated
The metric formula is:
MOD = ((ppO₂ ÷ FO₂) − 1) × 10 m
where ppO₂ is the oxygen partial-pressure limit (1.4 bar working, 1.6 bar contingency) and FO₂ is the fraction of oxygen in the mix (32% = 0.32). Dividing the limit by the fraction gives the absolute pressure in atmospheres where the limit is reached; subtracting the 1 atmosphere at the surface and multiplying by 10 m per atmosphere of seawater converts it to depth. In feet, the last step uses 33 ft per atmosphere.
Worked example for EAN32 at ppO₂ 1.4: (1.4 ÷ 0.32 − 1) × 10 = 33.75, rounded down to 33 m.
The calculator rounds down to the nearest metre and foot to stay conservative. Exceeding oxygen partial-pressure limits risks central nervous system oxygen toxicity, which can cause convulsions underwater. Always analyse your tank yourself, label it, and plan your MOD as you were taught in your nitrox course.