Nitrox Blend Calculator

Nitrox (EANx) replaces some of the nitrogen in your breathing gas with extra oxygen, which reduces nitrogen loading but tightens your oxygen exposure limits — this calculator works out both sides of that trade. Maximum Operating Depth (MOD) comes from your oxygen fraction and chosen ppO2 ceiling: MOD = (ppO2 limit ÷ fO2 − 1) × 10, the depth at which your oxygen partial pressure hits the limit you set (1.4 bar is the standard recreational ceiling, 1.6 bar for planned decompression). Equivalent Air Depth (EAD) answers a different question — at your planned depth, what depth would produce the same nitrogen partial pressure if you were breathing ordinary air (79% nitrogen)?

That lets you safely apply standard air dive tables to a Nitrox dive by using the shallower EAD instead of your true depth. The calculator also reports the "best mix" — the oxygen percentage that would put your ppO2 limit exactly at your planned depth, useful when deciding what blend to have filled — and estimates a single-exposure CNS oxygen toxicity time limit by stepping through NOAA's published ppO2-to-duration bands (for example, 150 minutes at 1.4 bar, dropping to 45 minutes at 1.6 bar); because this table is applied in discrete steps rather than a continuous curve, treat the CNS figure as a rough guide rather than a precise limit. As always, verify your actual blend with an oxygen analyzer before diving — never trust a label alone — and never exceed your certification's authorized ppO2 and MOD limits.