Nitrox Dive Calculator
Calculate PPO2, MOD, and EAD for Enriched Air Nitrox (EANx). Always verify with your training agency tables/computer.
Best Mix Finder
Find the oxygen percentage that gives your target PPO2 at depth.
What a Nitrox Calculator Helps You Plan
A nitrox calculator is a practical planning tool for divers using enriched air blends such as EAN28, EAN32, or EAN36. It helps you answer key pre-dive questions quickly: “What is my maximum operating depth?”, “What PPO2 will I hit at this depth?”, and “What is my equivalent air depth for no-decompression planning?”
While it does not replace formal training or a dive computer, it helps you make safer, more informed choices before entering the water.
Key Terms You Should Know
FO₂ (Fraction of Oxygen)
The oxygen percentage in your breathing gas. Air is approximately 21% oxygen; nitrox has more.
PPO₂ (Partial Pressure of Oxygen)
PPO2 increases with depth. If PPO2 gets too high, central nervous system oxygen toxicity risk increases. Recreational working limits commonly use 1.4 ata, with 1.6 ata treated as a contingency ceiling.
MOD (Maximum Operating Depth)
The deepest depth at which your chosen mix stays at or below your selected PPO2 limit.
EAD (Equivalent Air Depth)
A way to compare nitrogen exposure from nitrox to the depth you would have needed if breathing air. Lower EAD generally means more favorable no-decompression limits compared to air at the same actual depth.
How the Calculator Computes Results
- Ambient pressure: (depth / 33) + 1 in feet, or (depth / 10) + 1 in meters
- PPO₂ at depth: FO₂ × ambient pressure
- MOD: ((PPO₂ limit / FO₂) - 1) × 33 (or ×10 metric)
- EAD: (((depth + surface factor) × (1 - FO₂)) / 0.79) - surface factor
The logic is standard for recreational nitrox planning and can be used as a quick cross-check alongside your course materials.
Practical Example
Suppose you use EAN32 at 100 ft with a PPO2 limit of 1.4:
- PPO2 is about 1.29 ata (comfortable below 1.4)
- MOD at 1.4 is around 111 ft
- EAD is significantly shallower than 100 ft on air
This is exactly why nitrox is popular for repetitive dives and dives in the moderate depth range.
Best Practices for Safe Nitrox Use
- Analyze every cylinder yourself and label it clearly.
- Set your dive computer to the exact FO₂ before diving.
- Respect your MOD—never exceed it.
- Use conservative ascent rates and safety stops.
- Stay within your certification level and agency standards.
Common Mistakes Divers Make
- Confusing EAN32 with EAN36 during tank swaps
- Forgetting to update computer settings between dives
- Planning with one PPO2 limit but diving with another
- Ignoring workload, temperature, and CO2 factors that can raise oxygen risk
Final Note
This nitrox calculator is intended as an educational planning aid. It does not replace qualified instruction, local procedures, or your dive computer’s real-time guidance. If there is any conflict between tools, always default to the most conservative safe option.