Nitrox Calculator
MOD, EAD, best mix and O₂ toxicity — real-time calculations to plan your nitrox dives safely.
How to calculate MOD (Maximum Operating Depth) on nitrox?
The MOD (Maximum Operating Depth) is the deepest you can go with a given nitrox mix at a defined maximum PPO₂. It is calculated using the formula: MOD = ((PPO₂ / FO₂) − 1) × 10. For example, for an EANx32 with a max PPO₂ of 1.4 bar, the MOD is ((1.4 / 0.32) − 1) × 10 = 33.75 m.
What is EAD (Equivalent Air Depth)?
EAD (Equivalent Air Depth) is the depth on air that would produce the same narcosis and nitrogen loading as a nitrox dive at a given depth. The higher your FO₂, the lower the EAD — which extends no-decompression limits. Formula: EAD = ((FO₂ / 0.21) × (P + 10)) − 10.
O₂ toxicity and the NOAA table: understanding CNS %
Prolonged exposure to high PPO₂ can cause central nervous system (CNS) toxicity, manifesting as convulsions. The NOAA table defines maximum exposure durations for each PPO₂ level. Cumulative CNS % lets you track exposure over a day of diving. It is recommended not to exceed 80% CNS per day and 100% cumulatively.
Which nitrox mix should I choose for my dive?
The best mix is the one whose MOD exactly matches your target depth at a chosen max PPO₂. This is known as the "optimal mix". In practice, divers choose between EANx32 (nitrox 32%) and EANx36 for most reef dives between 20 and 35 m. Beyond 40% FO₂, oxygen toxicity risks increase significantly.
Nitrox experiences to book
Nitrox dives and courses available on Aster by Orque.
Journée de plongée sur l'île de Pianosa
Procchio - Marciana, Italie
Plongées raies aigles léopard
Playa del Carmen, Mexique
Plongée avec des requins bouledogues
Quintana Roo, Mexique
PADI Wreck Diver
Playa del Carmen, Mexique