Gas Viscosity Calculator

Enter temperature to compute gas dynamic (absolute) viscosity.
Air, natural gas, hydrocarbon vapor, ammonia, carbon dioxide, carbon monoxide, hydrogen, nitrogen, sulfur dioxide.

 Select gas: Standard Air Ammonia, NH3 Carbon Dioxide, CO2 Carbon Monoxide, CO Hydrocarbon vapor, SG=1 Hydrocarbon vapor, SG=.75 Hydrocarbon vapor, SG=.5 Hydrogen, H2 Natural gas, SG=1 Natural gas, SG=.75 Natural gas, SG=.5 Nitrogen, N2 Oxygen, O2 Sulfur Dioxide, SO2 Temperature: Celsius Kelvin Fahrenheit Rankine Viscosity: lb-s/ft2, slug/ft-s N-s/m2, kg/m-s poise, p centiPoise, cp © 2013 LMNO Engineering, Research, and Software, Ltd. www.LMNOeng.com

Units in gas viscosity calculation:
oC=degrees Celsius, K=Kelvin, oF=degrees Fahrenheit, oR=degrees Rankine, lb-s/ft2=pound-second per square foot, slug/ft-s=slug per foot per second, N-s/m2=Newton-second per square meter, kg/m-s=kilogram per meter per second, SG=specific gravity

The viscosity on this page is the dynamic (absolute) viscosity. Dynamic viscosity of gases is primarily a function of temperature. This variation is provided in Crane (1988) as a graph for hydrocarbon vapors and natural gases, and as an equation for other common gases. The impact of pressure is minor and the viscosity correction for pressure is less than 10% for the gases in our calculation for pressures up to 500 psi (34.5 bar) (Crane, 1988).

Hydrocarbon vapors and natural gases
The LMNO Engineering calculation takes the user input temperature and extracts viscosity from the graph on page A-5 in Crane (1988), performing linear interpolation if needed. The input temperature is restricted to the range 0 < temperature < 1000oF.

Other gases
Gas viscosity is computed using Sutherland's formula (Crane, 1988):

μ = μo*(a/b)*(T/To)3/2

a = 0.555To + C
b = 0.555T + C

where
μ  = viscosity in centipoise at input temperature T
μo = reference viscosity in centipoise at reference temperature To
T   = input temperature in degrees Rankine
To = reference temperature in degrees Rankine
C  = Sutherland's constant

The following table gives the values of Sutherland's constant and the reference temperature and viscosity for the gases used in the LMNO Engineering calculation. Values of Sutherland's constant are from Crane (1988, p.A-5). The reference temperatures and viscosities were selected from CRC (1984, pp.F-42-44).

 Sutherland's constant, C To (oR) μo (centipoise) standard air 120 524.07 0.01827 ammonia, NH3 370 527.67 0.00982 carbon dioxide, CO2 240 527.67 0.01480 carbon monoxide, CO 118 518.67 0.01720 hydrogen, H2 72 528.93 0.00876 nitrogen, N2 111 540.99 0.01781 oxygen, O2 127 526.05 0.02018 sulfur dioxide, SO2 416 528.57 0.01254

Validity of gas viscosity equation

For hydrocarbon vapors and natural gases, input temperature T is restricted to the range
0 < temperature < 1000oF.

For other gases, input temperature must be at least absolute zero (0 K).

If the input temperature is outside the valid range, an error message is printed and viscosity is not computed.

The impact of pressure is minor, and the viscosity correction for pressure is less than 10% for the gases in our calculation for pressures up to 500 psi (34.5 bar) (Crane, 1988).

References for gas viscosity
Chemical Rubber Company (CRC). 1984. CRC Handbook of Chemistry and Physics. Weast, Robert C., editor. 65th edition. CRC Press, Inc. Boca Raton, Florida. USA.

Crane Company. 1988. Flow of fluids through valves, fittings, and pipe. Technical Paper No. 410 (TP 410).