A scuba nitrox calculator determines the maximum operating depth (MOD) for any enriched air blend. Breathing oxygen-rich nitrox deeper than the MOD risks oxygen toxicity — a sudden convulsion while underwater is almost always fatal. Always verify MOD before every dive and mark your tank accordingly.
Nitrox Mix Details
How to Calculate Nitrox MOD and Equivalent Air Depth
The nitrox MOD calculator protects you from oxygen toxicity by calculating the maximum depth at which your nitrox blend stays within safe oxygen partial pressure limits. This is the most critical calculation before every nitrox dive.
Step 1: Enter Your O₂ Percentage
Adjust the slider or type your exact mix percentage. Use the percentage that appears on your dive computer after you analyze the tank, not the blend you requested. Common recreational mixes: EAN32 (32% O₂) and EAN36 (36% O₂). Air is 21% O₂.
Step 2: Set Your ppO₂ Limit
Most recreational divers and agencies use 1.4 bar as the working limit for MOD, with 1.6 bar as the absolute maximum for short exposures. Setting 1.4 bar gives you a safety margin. Some technical divers use 1.2 bar for conservative calculations on long decompression dives.
Step 3: Understand MOD
The MOD formula is: MOD (m) = [ppO₂ / FO₂ − 1] × 10. For EAN32 at 1.4 bar ppO₂: [1.4/0.32 − 1] × 10 = 33.75m (approximately 34m or 111 feet). Never dive deeper than your MOD. Program your MOD into your dive computer before entering the water.
Step 4: Use Equivalent Air Depth for Tables
The equivalent air depth (EAD) lets you use standard air dive tables for your no-decompression limits. Since nitrox has less nitrogen, you accumulate nitrogen more slowly — EAD is always shallower than your actual depth. Use EAD with your PADI or NAUI recreational dive planner tables to find your actual NDL.
FAQ
Is this nitrox calculator free?
Yes, completely free with no signup required. Calculate MOD and EAD for any nitrox blend instantly.
Is my data safe and private?
Yes. All calculations run locally in your browser. No data is sent to any server.
What is nitrox and why do scuba divers use it?
Nitrox (enriched air) is a breathing gas with more than 21% oxygen and less nitrogen than normal air. The reduced nitrogen extends no-decompression limits — you can stay longer at depth before accumulating too much nitrogen. Common mixes are EAN32 (32% O2) and EAN36 (36% O2). Nitrox requires special training and equipment certification.
What is maximum operating depth (MOD)?
MOD is the deepest safe depth for a given nitrox mixture based on a maximum partial pressure of oxygen (ppO2). Most recreational divers use 1.4 bar ppO2 as the limit (1.6 bar for short exposures). Exceeding MOD risks oxygen toxicity convulsions — unconsciousness underwater with a regulator in your mouth is fatal.
What is the MOD for EAN32 (32% nitrox)?
EAN32 has a MOD of approximately 111 feet (34m) at 1.4 bar ppO2, or 130 feet (40m) at 1.6 bar. For comparison, air (21% O2) has a MOD of 187 feet (57m) at 1.4 bar — this is why you can breathe air deeper than nitrox before hitting oxygen toxicity limits.
What is equivalent air depth (EAD)?
EAD is the depth at which you would accumulate the same nitrogen while breathing air as you would at your actual depth breathing nitrox. EAD is always shallower than your real depth when using nitrox mixes. Use your EAD with standard air dive tables to determine no-decompression limits and surface intervals.