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Gas Density Calculator

The Gas Density Calculator helps divers estimate the density of breathing gases, such as Nitrox, at different depths and temperatures. Monitoring gas density is essential for planning mixes that reduce breathing resistance and minimise CO₂ retention, ensuring better comfort and efficiency during deeper dives.

Current research recommends a maximum breathing gas density of 5.2 g/L (0.325 lb/ft³), with an advised absolute maximum of 6.2 g/L (0.387 lb/ft³).

Depth (ft)

Temperature (F)

Gas oxygen content (O₂) %

Helium content (He) %

The gas density at 115 ft with 32% O₂ and 0% He is approximately 0.337 lb/cu ft

Note: All calculations run in metric (m, °C, g/L) then convert to your selected units.


The gas density is calculated using the ideal gas law:

ρ = (P · M) / (R · T)

Where:

  • P = absolute pressure at depth in atm (1 + depth/10)
  • M = average molar mass of the gas mixture (g/mol)
  • R = universal gas constant (8.314 J/(mol·K))
  • T = temperature in Kelvin (Celsius + 273.15)

Step-by-step:

  1. Compute pressure: Patm = 1 + depth/10 = 4.51 atm; PPa = Patm × 101325 = 456489 Pa
  2. Calculate average molar mass:
    M = O₂% × 32 + N₂% × 28 + He% × 4 = 29.28 g/mol
  3. Convert M to kg/mol: 0.02928 kg/mol
  4. Convert T to Kelvin: 25.00 + 273.15 = 298.15 K
  5. Raw density: ρ = (PPa × Mkg/mol) / (R × T) = 5.397 g/L

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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.