Dynamic viscosity is a material property which describes the resistance of a fluid to shearing flows. It corresponds roughly to the intuitive notion of a fluid's 'thickness'. For instance, honey has a much higher viscosity than water. Viscosity is measured using a viscometer. Measured values span several orders of magnitude. Of all fluids, gases have the lowest viscosities, and thick liquids have the highest. There is evidence of solid flow as result of Brownian motion in condition of extremes such as high temperature, high pressure, and extremely long time scales as theorized for the motion of the Earth's solid metal core.
The values listed in this article are representative estimates only, as they do not account for measurement uncertainties, variability in material definitions, or non-Newtonian behavior.
Kinematic viscosity is dynamic viscosity divided by fluid mass density. This page lists only dynamic viscosity.
Units and conversion factors For dynamic viscosity, the SI unit is Pascal-second. In engineering, the unit is usually Poise or centiPoise, with 1 Poise = 0.1 Pascal-second, and 1 centiPoise = 0.01 Poise.
For kinematic viscosity, the SI unit is m^2/s. In engineering, the unit is usually Stoke or centiStoke, with 1 Stoke = 0.0001 m^2/s, and 1 centiStoke = 0.01 Stoke.
For liquid, the dynamic viscosity is usually in the range of 0.001 to 1 Pascal-second, or 1 to 1000 centiPoise. The density is usually on the order of 1000 kg/m^3, i.e. that of water. Consequently, if a liquid has dynamic viscosity of n centiPoise, and its density is not too different from that of water, then its kinematic viscosity is around n centiStokes.
For gas, the dynamic viscosity is usually in the range of 10 to 20 microPascal-seconds, or 0.01 to 0.02 centiPoise. The density is usually on the order of 0.5 to 5 kg/m^3. Consequently, its kinematic viscosity is around 2 to 40 centiStokes.
Viscosities at or near standard conditions
Here "standard conditions" refers to temperatures of 25 °C and pressures of 1 atmosphere. Where data points are unavailable for 25 °C or 1 atmosphere, values are given at a nearby temperature/pressure.
The temperatures corresponding to each data point are stated explicitly. By contrast, pressure is omitted since gaseous viscosity depends only weakly on it.
Gases Noble gases The simple structure of noble gas atoms makes them amenable to accurate theoretical treatment. For this reason, measured viscosities of the noble gases serve as important tests of the kinetic-molecular theory of transport processes in gases (see Chapman–Enskog theory). One of the key predictions of the theory is the following relationship between viscosity , thermal conductivity , and specific heat :
where is a constant which in general depends on the details of intermolecular interactions, but for spherically symmetric species is very close to .
This prediction is reasonably well-verified by experiments, as the following table shows. Indeed, the relation provides a viable means for obtaining thermal conductivities of gases since these are more difficult to measure directly than viscosity. SubstanceMolecular formulaViscosity (μPa·s)Thermal conductivity (W m−1K−1)Specific heat (J K−1kg−1)NotesRefs.HeliumHe19.850.15331162.47NeonNe31.750.04926182.51ArgonAr22.610.01783132.52KryptonKr25.380.00941492.49XenonXe23.080.005695.02.55RadonRn≈26≈0.0036456.2T = 26.85 °C; calculated theoretically; estimated assuming
Diatomic elements SubstanceMolecular formulaViscosity (μPa·s)NotesRef.HydrogenH28.90NitrogenN217.76OxygenO220.64FluorineF223.16 ChlorineCl213.40
Hydrocarbons SubstanceMolecular formulaViscosity (μPa·s)NotesRef.MethaneCH411.13T = 20 °CAcetyleneC2H2 10.2T = 20 °CEthyleneC2H4 10.28T = 20 °CEthaneC2H69.27T = 20 °CPropyneC3H4 8.67T = 20 °CPropeneC3H6 8.39T = 20 °CPropaneC3H8 8.18T = 20 °CButaneC4H10 7.49T = 20 °C
Organohalides
SubstanceMolecular formulaViscosity (μPa·s)NotesRef.Carbon tetrafluorideCF417.32FluoromethaneCH3F11.79DifluoromethaneCH2F212.36FluoroformCHF314.62PentafluoroethaneC2HF512.94HexafluoroethaneC2F6 14.00OctafluoropropaneC3F812.44
Other gases
SubstanceMolecular formulaViscosity (μPa·s)NotesRef.Air18.46AmmoniaNH310.07Nitrogen trifluorideNF317.11T = 26.85 °CBoron trichlorideBCl312.3Theoretical estimate at T = 26.85 °C; estimated uncertainty of 10%Carbon dioxideCO214.90Carbon monoxideCO17.79Hydrogen sulfideH2S12.34Nitric oxideNO18.90Nitrous oxideN2O14.90Sulfur dioxideSO212.82Sulfur hexafluorideSF615.23Molybdenum hexafluorideMoF614.5Theoretical estimates at T = 26.85 °CTungsten hexafluorideWF617.1Uranium hexafluorideUF617.4
Liquids
n-Alkanes Substances composed of longer molecules tend to have larger viscosities due to the increased contact of molecules across layers of flow. This effect can be observed for the n-alkanes and 1-chloroalkanes tabulated below. More dramatically, a long-chain hydrocarbon like squalane (C30H62) has a viscosity an order of magnitude larger than the shorter n-alkanes (roughly 31 mPa·s at 25 °C). This is also the reason oils tend to be highly viscous, since they are usually composed of long-chain hydrocarbons.
SubstanceMolecular formulaViscosity (mPa·s)NotesRef.PentaneC5H120.224HexaneC6H140.295HeptaneC7H160.389OctaneC8H180.509NonaneC9H200.665DecaneC10H220.850UndecaneC11H241.098DodecaneC12H261.359TridecaneC13H281.724TetradecaneC14H302.078PentadecaneC15H322.82T = 20 °CHexadecaneC16H343.03HeptadecaneC17H364.21T = 20 °C
1-Chloroalkanes SubstanceMolecular formulaViscosity (mPa·s)NotesRef.ChlorobutaneC4H9Cl0.4261ChlorohexaneC6H11Cl0.6945ChlorooctaneC8H17Cl1.128ChlorodecaneC10H21Cl1.772ChlorododecaneC12H25Cl2.668ChlorotetradecaneC14H29Cl3.875ChlorohexadecaneC16H33Cl5.421ChlorooctadecaneC18H37Cl7.385Supercooled liquid
Other halocarbons SubstanceMolecular formulaViscosity (mPa·s)NotesRef.DichloromethaneCH2Cl20.401Trichloromethane (chloroform)CHCl30.52Tribromomethane (bromoform)CHBr31.89Carbon tetrachlorideCCl40.86TrichloroethyleneC2HCl3 0.532TetrachloroethyleneC2Cl4 0.798T = 30 °CChlorobenzeneC6H5Cl0.773BromobenzeneC6H5Br1.0801-BromodecaneC10H21Br3.373
Alkenes SubstanceMolecular formulaViscosity (mPa·s)NotesRef.2-PenteneC5H100.2011-HexeneC6H120.2711-HepteneC7H140.3621-OcteneC8H160.506T = 20 °C2-OcteneC8H160.506T = 20 °Cn-DeceneC10H200.828T = 20 °C
Other liquids SubstanceMolecular formulaViscosity (mPa·s)NotesRef.Acetic acidC2H4O21.056AcetoneC3H6O0.302BenzeneC6H60.604BromineBr20.944EthanolC2H6O1.074GlycerolC3H8O31412HydrazineH4N20.876Iodine pentafluorideIF52.111MercuryHg1.526MethanolCH4O0.5531-Propanol (propyl alcohol) C3H8O1.9452-Propanol (isopropyl alcohol) C3H8O2.052SqualaneC30H62 31.123WaterH2O1.0016T = 20 °C, standard pressure
Aqueous solutions The viscosity of an aqueous solution can either increase or decrease with concentration depending on the solute and the range of concentration. For instance, the table below shows that viscosity increases monotonically with concentration for sodium chloride and calcium chloride, but decreases for potassium iodide and cesium chloride (the latter up to 30% mass percentage, after which viscosity increases).
The increase in viscosity for sucrose solutions is particularly dramatic, and explains in part the common experience of sugar water being "sticky".
Table: Viscosities (in mPa·s) of aqueous solutions at T = 20 °C for various solutes and mass percentagesCRC Handbook of Chemistry and Physics, 99th Edition (Internet Version 2018), John R. Rumble, ed., CRC Press/Taylor & Francis, Boca Raton, FL. Solute mass percentage = 1% 2% 3% 4% 5% 10% 15% 20% 30% 40% 50% 60% 70% Sodium chloride (NaCl)1.0201.0361.0521.0681.0851.1931.3521.557 Calcium chloride (CaCl2)1.028 1.0501.0781.1101.1431.3191.5641.9303.4678.997 Potassium iodide (KI)0.9970.9910.9860.9810.9760.9460.9250.9100.8920.897 Cesium chloride (CsCl)0.9970.9920.9880.9840.9800.9660.9530.9390.9220.9340.9811.120 Sucrose (C12H22O11)1.0281.0551.0841.1141.1461.3361.5921.9453.1876.16215.43158.487481.561
Substances of variable composition
SubstanceViscosity (mPa·s)Temperature (°C)ReferenceWhole milk2.1220Blood2 - 937Olive oil56.229Canola oil46.230Sunflower oil48.826Honey 2000-10,00020Ketchup 5000-20,00025Peanut butter 104-106Pitch10-30 (variable)
Viscosities under nonstandard conditions
Gases
All values are given at 1 bar (approximately equal to atmospheric pressure).
SubstanceChemical formulaTemperature (K)Viscosity (μPa·s) Air 100 7.1 200 13.3 300 18.5 400 23.1 500 27.1 600 30.8 Ammonia NH3 300 10.2 400 14.0 500 17.9 600 21.7 Carbon dioxide CO2 200 10.1 300 15.0 400 19.7 500 24.0 600 28.0 Helium He 100 9.6 200 15.1 300 19.9 400 24.3 500 28.3 600 32.2 Water vapor H2O 380 12.498 400 13.278 450 15.267 500 17.299 550 19.356 600 21.425 650 23.496 700 25.562 750 27.617 800 29.657 900 33.680 1000 37.615 1100 41.453 1200 45.192
Liquids (including liquid metals)
SubstanceChemical formulaTemperature (°C)Viscosity (mPa·s) Mercury Hg -30 1.958 -20 1.856 -10 1.766 0 1.686 10 1.615 20 1.552 25 1.526 30 1.495 50 1.402 75 1.312 100 1.245 126.85 1.187 226.85 1.020 326.85 0.921 Ethanol C2H6O -25 3.26 0 1.786 25 1.074 50 0.694 75 0.476 Bromine Br2 0 1.252 25 0.944 50 0.746 Water H2O 0.01 1.7911 10 1.3059 20 1.0016 25 0.89002 30 0.79722 40 0.65273 50 0.54652 60 0.46603 70 0.40355 80 0.35405 90 0.31417 99.606 0.28275 Glycerol C3H8O3 25 934 50 152 75 39.8 100 14.76 Aluminum Al 700 1.24 800 1.04 900 0.90 Gold Au 1100 5.130 1200 4.640 1300 4.240 Copper Cu 1100 3.92 1200 3.34 1300 2.91 1400 2.58 1500 2.31 1600 2.10 1700 1.92 Silver Ag 1300 3.75 1400 3.27 1500 2.91 Iron Fe 1600 5.22 1700 4.41 1800 3.79 1900 3.31 2000 2.92 2100 2.60
In the following table, the temperature is given in kelvins.
SubstanceChemical formulaTemperature (K)Viscosity (mPa·s) Gallium Ga 400 1.158 500 0.915 600 0.783 700 0.700 800 0.643 Zinc Zn 700 3.737 800 2.883 900 2.356 1000 2.005 1100 1.756 Cadmium Cd 600 2.708 700 2.043 800 1.654 900 1.403
Solids
SubstanceViscosity (Pa·s)Temperature (°C)granite - 25asthenosphere900upper mantle – 1300–3000lower mantle – 3000–4000
References