MOD & END Calculator
Two related calculators for gas-mix depth planning. Maximum Operating Depth caps your O₂ exposure; Equivalent Narcotic Depth tells you how "thick" the gas feels at depth.
Checking — from the gas blender — the mix is pre-filled in both calculators below.
Maximum Operating Depth
Deepest you can breathe this mix before PPO₂ exceeds the safety limit.
Result
Maximum Operating Depth
— m
Mix at this depth: — PPO₂. Beyond this depth, oxygen toxicity risk rises sharply.
Equivalent Narcotic Depth
For trimix. Tells you the depth at which air would feel equally narcotic.
Result
Equivalent Narcotic Depth
— m
At — m on this mix, narcotic load matches air at the END above. Targets: keep END at or below 30 m for routine tech, 40 m max.
Common questions
How do you calculate maximum operating depth (MOD)?
MOD in metres equals (your PO2 limit divided by the gas oxygen fraction, minus 1) times 10. For EAN32 at a 1.4 bar limit that is about 33 m. 1.4 bar is the usual working limit and 1.6 bar the absolute ceiling.
What is equivalent narcotic depth (END)?
END is the depth of an air dive that would feel as narcotic as your trimix at depth. Replacing nitrogen with helium lowers the END, which is why technical divers add helium for deep dives.
What PO2 should I use for MOD?
1.4 bar for the active, working part of a dive, and 1.6 bar as an absolute ceiling used only briefly at rest on a decompression stop. This tool lets you set the ceiling so you can plan to either.