Density of some common Gases

Densities and molecular weights of common gases like acetylene, air, methane, nitrogen, oxygen and others.

Gases and their properties

Hydrogen(H2)
Molecular weight: 2.016
Density (kg/m3): 0.08992
Density (lb/ft3): 0.00562

Helium(He)
Molecular weight: 4.02
Density (kg/m3): 0.16641 / 0.17852
Density (lb/ft3): 0.010391 / 0.0111432

Methane(CH4)
Molecular weight: 16.043
Density (kg/m3):0.6681 / 0.7172
Density (lb/ft3): 0.04171 / 0.04472

Ammonia(NH3)
Molecular weight: 17.031
Density (kg/m3): 0.7171 / 0.7692
Density (lb/ft3): 0.04481 / 0.04802

Water Vapor, steam(H2O)
Molecular weight: 18.016
Density (kg/m3): 0.804
Density (lb/ft3): 0.048

Natural gas
Molecular weight: 19.5
Density (kg/m3): 0.7 – 0.92
Density (lb/ft3): 0.044 – 0.0562

Neon(Ne)
Molecular weight: 20.179
Density (kg/m3): 0.89992
Density (lb/ft3): 0.0561792

Acetylene/ethyne(C2H2)
Molecular weight: 26
Density (kg/m3): 1.0921 / 1.1702
Density (lb/ft3): 0.06821 / 0.07292

Carbon monoxide(Co)
Molecular weight: 28.01
Density (kg/m3): 1.1651 / 1.2502
Density (lb/ft3):0.07271 /0.07802

Nitrogen(N)
Molecular weight: 28.02
Density (kg/m3): 1.1651 / 1.25062
Density (lb/ft3): 0.07271 /0.0780722

Ethylene(C2H4)
Molecular weight: 28.03
Density (kg/m3): 1.2602
Density (lb/ft3):0.07862

Air
Molecular weight: 29
Density (kg/m3):1.2051 /1.2932
Density (lb/ft3): 0.07521/0.08062

Nitric oxide(NO)
Molecular weight:30.0
Density (kg/m3): 1.2491
Density (lb/ft3): 0.07801

Ethane(C2H6)
Molecular weight:30.07
Density (kg/m3):1.2641
Density (lb/ft3): 0.07891

Oxygen(O2)
Molecular weight:32
Density (kg/m3):1.3311
1.42902
Density (lb/ft3): 0.08311
0.0892102

Methyl Alcohol
Molecular weight:32.04

Sulfur
Molecular weight: 32.06
Density (lb/ft3): 0.135

Hydrogen Sulfide
Molecular weight:34.076
Density (kg/m3):1.4341
Density (lb/ft3):0.08951

Hydrochloric Acid
Molecular weight:36.47
Density (kg/m3):1.632

Hydrogen Chloride(HCl)
Molecular weight:36.5
Density (kg/m3):1.5281
Density (lb/ft3):0.09541

Argon(Ar)
Molecular weight:39.948
Density (kg/m3):1.6611
1.78372
Density (lb/ft3):0.10371
0.1113532

Propene /propylene(C3H6)
Molecular weight:42.1
Density (kg/m3):1.7481
Density (lb/ft3):0.10911

Carbon dioxide
Molecular weight:44.01
Density (kg/m3): 1.8421
1.9772
Density (lb/ft3):0.11501
0.12342

Nitrous Oxide(NO2)
Molecular weight:44.013
Density (lb/ft3):0.1141

Propane(C3H8)
Molecular weight:44.09
Density (kg/m3):1.8821
Density (lb/ft3):0.11751

Nitrogen Dioxide
Molecular weight:46.006

Ethyl Alcohol
Molecular weight: 46.07

OzoneO3
Molecular weight:48.0
Density (kg/m3):2.142
Density (lb/ft3):0.125

Sulfuric Oxide
Molecular weight:48.063

Methyl Chloride
Molecular weight: 50.49

Butylene (Butene)
Molecular weight:56.11
Density (kg/m3):2.504
Density (lb/ft3):0.1482

Butane
Molecular weight:56.11
Density (kg/m3):2.4891
2.52
Density (lb/ft3):0.15541
0.1562

Nitrous Trioxide
Molecular weight:62.005

Sulfur Dioxide
Molecular weight:64.06
Density (kg/m3):2.2791
2.9262
Density (lb/ft3):0.17031
0.18282

Ethyl Chloride
Molecular weight:64.52

Chlorine
Molecular weight:70.906
Density (kg/m3):2.9941
Density (lb/ft3):0.18691

Methyl Butane
Molecular weight:72.15

N-Pentane
Molecular weight:72.15

Iso-Pentane
Molecular weight:72.15

Carbon disulphide
Molecular weight:76.13

Benzene
Molecular weight:78.11
Density (kg/m3):3.486
Density (lb/ft3):0.20643

Sulfur Trioxide
Molecular weight:80.062

Cyclohexane
Molecular weight:84.16

Hexane
Molecular weight:86.17

R-22
Molecular weight:86.48

Toluene
Molecular weight:92.141
Density (kg/m3):4.111
Density (lb/ft3):0.2435

N-Heptane
Molecular weight:100.20

R-134a
Molecular weight:102.03

N-Octane
Molecular weight: 114.22

R-12
Molecular weight: 120.92

R-11
Molecular weight: 137.37

R-123
Molecular weight: 152.93

R-114
Molecular weight: 170.93

Blast furnace gas
Density (kg/m3):1.2502
Density (lb/ft3):0.07802

Carbureted Water Gas
Density (lb/ft3): 0.048

Coal gas
Density (kg/m3): 0.582

Coke Oven Gas
Density (lb/ft3): 0.0342

Combustion products
Density (kg/m3):1.112
Density (lb/ft3):0.0692

Digester Gas (Sewage or Biogas)
Density (lb/ft3): 0.062

Krypton
Density (kg/m3): 3.742

Sasol
Density (lb/ft3): 0.032

Water gas (bituminous)
Density (lb/ft3): 0.054

Xenon
Density (kg/m3): 5.862

1. NTP – Normal Temperature and Pressure – is defined as 20oC (293.15 K, 68oF) and 1 atm ( 101.325 kN/m2, 101.325 kPa, 14.7 psia, 0 psig, 30 in Hg, 760 torr)
2. STP – Standard Temperature and Pressure – is defined as 0oC (273.15 K, 32oF) and 1 atm (101.325 kN/m2, 101.325 kPa, 14.7 psia, 0 psig, 30 in Hg, 760 torr)

• 1 lbm/ft3 = 16.018 kg/m3

• 1 kg/m3 = 0.0624 lbm/ft3

Note that even if pounds per cubic foot is often used as a measure of density in the U.S., pounds are really a measure of force, not mass. Slugs are the correct measure of mass. You can divide pounds per cubic foot by 32.2 for a rough value in slugs.