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Equivalent Narcotic Depth Calculator

The Equivalent Narcotic Depth (END) Calculator helps technical divers estimate the narcotic impact of a given gas mix. By calculating END, divers can better understand and mitigate the effects of nitrogen narcosis, leading to safer and more informed dive planning.

Depth (ft)

Gas oxygen content (O₂) %

Helium content (He) %

The Equivalent Narcotic Depth (END) for 98 ft with 21% O₂ and 0% He is approximately 98.1 ft

Note: END is computed in metric, then converted to your preferred unit.


The Equivalent Narcotic Depth is calculated with:


END = (D + 10) × (fO₂ + fN₂) − 10

Where:

  • D = depth in meters
  • fO₂ = O₂ fraction (e.g., 0.21)
  • fN₂ = N₂ fraction = 1 − fO₂ − fHe

Steps:

  1. Compute fractions: fO₂ = 0.21, fHe = 0.00, fN₂ = 0.79
  2. Calculate END: ( 29.87 + 10 ) × 1.00 − 10 = 29.90 m
  3. Convert to display unit: 98.1 ft

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Important Warning: The calculators provided on this page are intended for reference purposes only. While we strive for accuracy, divers are strongly advised to verify the output of these calculators independently before use. Always double-check calculations and consider all safety factors relevant to your specific diving conditions and experience level. Diving without proper verification and planning can be dangerous. Dive safely and responsibly.