Inputs

Units:

Imperial Metric

Maximum depth

Target ppO₂

ata

1.4 ata at the working depth is a common tech target.

Target END (max equivalent narcotic depth)

100 ft / 30 m is a common tech ceiling for narcosis.

Target gas density (max)

g/L

5.2 g/L recommended (Anthony & Mitchell, 2016); 6.2 g/L hard ceiling.

Treat O₂ as narcotic (modern convention: yes)

Recommended Mix

O₂ fraction

—

N₂ fraction

—

He fraction

—

At your maximum depth

Constraint	Target	Achieved	Status

How the math works: For the chosen depth, FO₂ is set to deliver the target ppO₂ exactly, then the algorithm finds the smallest helium fraction that keeps both the END and the gas density at or below their targets. If both targets are already satisfied without helium, a nitrox mix is recommended. Density uses 0°C reference values (O₂ 1.429, N₂ 1.251, He 0.179 g/L).