μ = dynamic viscosity of fluid (N s/m 2 )
dc = unit velocity (m/s)
dy = unit distance between layers (m)
γ = dc / dy = shear rate (s -1 )
Equation (1) is known as the Newtons Law of Friction.
(1) can be rearranged to express Dynamic viscosity as
μ = τ dy / dc
= τ / γ (1b)
In the SI system the dynamic viscosity units are N s/m 2 , Pa s or kg/(m s) - where
Dynamic viscosity may also be expressed in the metric CGS (centimeter-gram-second) system as g/(cm s) , dyne s/cm 2 or poise (p) where
For practical use the Poise is normally too large and the unit is therefore often divided by 100 - into the smaller unit centipoise (cP) - where
Water at 20.2 o C (68.4 o F) has the absolute viscosity of one - 1 - centiPoise .
|Liquid||Absolute Viscosity *) |
( N s/m 2 , Pa s)
|Air||1.983 10 -5|
|Olive Oil||10 -1|
|Liquid Honey||10 1|
|Golden Syrup||10 2|
*) at room temperature
Kinematic viscosity is the ratio of - absolute (or dynamic) viscosity to density - a quantity in which no force is involved. Kinematic viscosity can be obtained by dividing the absolute viscosity of a fluid with the fluid mass density like
ν = μ / ρ (2)
ν = kinematic viscosity (m 2 /s)
μ = absolute or dynamic viscosity (N s/m 2 )
ρ = density (kg/m 3 )
In the SI-system the theoretical unit of kinematic viscosity is m 2 /s - or the commonly used Stoke (St) where
Stoke comes from the CGS (Centimetre Gram Second) unit system.
Since the Stoke is a large unit it is often divided by 100 into the smaller unit centiStoke (cSt) - where
The specific gravity for water at 20.2 o C (68.4 o F) is almost one, and the kinematic viscosity for water at 20.2 o C (68.4 o F) is for practical purpose 1.0 mm 2 /s ( cStokes). A more exact kinematic viscosity for water at 20.2 o C (68.4 o F) is 1.0038 mm 2 /s (cSt).
A conversion from absolute to kinematic viscosity in Imperial units can be expressed as
ν = 6.7197 10 -4 μ / γ (2a)
ν = kinematic viscosity (ft 2 /s)
μ = absolute or dynamic viscosity (cP)
γ = specific weight (lb/ft 3 )
The viscosity of a fluid is highly temperature dependent - and for dynamic or kinematic viscosity to be meaningful the reference temperature must be quoted. In ISO 8217 the reference temperature for a residual fluid is 100 o C . For a distillate fluid the reference temperature is 40 o C .
This is a free app that can be used offline on mobile devices.
Saybolt Universal Seconds (or SUS ) is an alternative unit for measuring viscosity. The efflux time is Saybolt Universal Seconds ( SUS ) required for 60 milliliters of a petroleum product to flow through the calibrated orifice of a Saybolt Universal viscometer - under a carefully controlled temperature and as prescribed by test method ASTM D 88. This method has largely been replaced by the kinematic viscosity method. Saybolt Universal Seconds is also called the SSU number (Seconds Saybolt Universal) or SSF number (Saybolt Seconds Furol) .
Kinematic viscosity in SSU versus dynamic or absolute viscosity can be expressed as
ν SSU = B μ / SG
= B ν centiStokes (3)
ν SSU = kinematic viscosity (SSU)
B = 4.632 for temperature 100 o F (37.8 o C)
B = 4.664 for temperature 210 o F (98.9 o C)μ = dynamic or absolute viscosity (cP)
SG = Specific Gravity
ν centiStokes = kinematic viscosity (centiStokes)
Degree Engler is used in Great Britain as a scale to measure kinematic viscosity. Unlike the Saybolt and Redwood scales, the Engler scale is based on comparing the flow of the substance being tested to the flow of another substance - water. Viscosity in Engler degrees is the ratio of the time of a flow of 200 cubic centimeters of the fluid whose viscosity is being measured - to the time of flow of 200 cubic centimeters of water at the same temperature (usually 20 o C but sometimes 50 o C or 100 o C ) in a standardized Engler viscosity meter.
A fluid where the shearing stress is linearly related to the rate of shearing strain - is designated as a Newtonian Fluid.
A Newtonian material is referred to as true liquid since the viscosity or consistency is not affected by shear such as agitation or pumping at a constant temperature. Most common fluids - both liquids and gases - are Newtonian fluids. Water and oils are examples of Newtonian liquids.
A Shear-thinning or pseudo-plastic fluid is a fluid where the viscosity decrease with increased shear rate. The structure is time-independent.
A Thixotropic fluid has a time-dependent structure. The viscosity of a thixotropic fluid decreases with increasing time - at a constant shear rate.
Ketchup and mayonnaise are examples of thixotropic materials. They appear thick or viscous but are possible to pump quite easily.
A Shear Thickening Fluid - or Dilatant Fluid - increases the viscosity with agitation or shear strain. Dilatant fluids are known as non-Newton fluids.
Some dilatant fluids can become almost solid in a pump or pipe line. With agitation cream becomes butter and candy compounds. Clay slurry and similar heavily filled liquids do the same thing.
A Bingham Plastic Fluid has a yield value which must be exceeded before it will start to flow like a fluid. From that point the viscosity decreases with increasing agitation. Toothpaste, mayonnaise and tomato ketchup are examples of such products.
Kinematic viscosity of air at 1 bar (1 10 5 Pa, N/m 2 ) and 40 o C is 16.97 cSt (16.97 10 -6 m 2 /s) .
The density of the air can be estimated with the Ideal Gas Law
ρ = p / (R T)
= (1 10 5 N/m 2 ) / ( (287 J/(kg K)) ((273 o C) + (33 o C)) )
= 1.113 (kg/m 3 )
ρ = density (kg/m 3 )
p = absolute pressure (Pa, N/m 2 )
R = individual gas constant (J/(kg K))
T = absolute temperature (K)
The absolute viscosity can be calculated as
μ = 1.113 (kg/m 3 ) 16.97 10 -6 (m 2 /s)
= 1.88 10 -5 (kg/(m s), N s/m 2 )
(cSt, 10 -6 m 2 /s, mm 2 /s )
|Saybolt Second |
|1||31||Water (20 o C)|
SAE 20 Crankcase Oil
SAE 75 Gear Oil
|15.7||80||No. 4 fuel oil|
|110||500||SAE 30 Crankcase Oil |
SAE 85 Gear Oil
|220||1000||Tomato Juice |
SAE 50 Crankcase Oil
SAE 90 Gear Oil
|440||2000||SAE 140 Gear Oil|
|1100||5000||Glycerine (20 o C) |
SAE 250 Gear Oil
Kinematic viscosity can be converted from SSU to Centistokes with
ν Centistokes = 0.226 ν SSU - 195 / ν SSU (4)
ν SSU < 100
ν Centistokes = 0.220 ν SSU - 135 / ν SSU
ν SSU > 100
Kinematic viscosity of fluids like water, mercury, oils SAE 10 and oil no. 3 - and gases like air, hydrogen and helium are indicated in the diagram below. Note that
Three types of devices are used to measure viscosity
Pipe lines - fluid flow and pressure loss - water, sewer, steel pipes, pvc pipes, copper tubes and more.
The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.
Material properties of gases, fluids and solids - densities, specific heats, viscosities and more.
Piping systems and pumps - centrifugal pumps, displacement pumps - cavitation, viscosity, head and pressure, power consumption and more.
Viscosities of products and chemical species at varying conditions.
Convert between dynamic or absolute viscosity units - Poiseuille, Poise, centPoise and more.
Chemical, physical and thermal properties of acetone, also called 2-propanone, dimethyl ketone and pyroacetic acid. Phase diagram included.
Online calculator, figures and tables with dynamic (absolute) and kinematic viscosity for air at temperatures ranging -100 to 1600°C (-150 to 2900°F) and at pressures ranging 1 to 10 000 bara (14.5 - 145000 psia) - SI and Imperial Units.
Thermal properties of air at different temperatures - density, viscosity, critical temperature and pressure, triple point, enthalpi and entropi, thermal conductivity and diffusivity and more.
Online calculator, figures and tables showing dynamic (absolute) and kinematic viscosity of gasous and liquid ammonia at temperatures ranging from -73 to 425°C (-100 to 800°F) at pressure ranging from 1 to 1000 bara (14.5 - 14500 psia) - SI and Imperial Units.
Figures and table with changes in Prandtl number for ammonia with changes in temperature and pressure.
Online calculator, figures and table showing dynamic and kinematic viscosity of benzene, C6H6, at varying temperature and pressure - Imperial and SI Units.
Chemical, physical and thermal properties of benzene, also called benzol. Phase diagram included.
Online calculators, figures and tables with dynamic and kinematic viscosity of liquid and gaseous butane, C4H10, at varying temperarure and pressure, SI and Imperial units.
Hydrodynamic losses through pumps depends on fluid viscosities.
Viscosity at 20°C/68°F and 50°C/122°F for more than 120 crudes is shown as function of specific gravity@15°C/60°F.
Convert dynamic viscosity values between units like Poiseuille - Poise - centiPoise and more.
Calculate pressure loss - or head loss - in ducts, pipes or tubes.
Oil viscosity vs. temperature.
Online calculator, figures and tables showing dynamic and kinematic viscosity of ethanol, C2H5OH, at varying temperature and pressure - Imperial and SI Units.
Online calculator, figures and tables showing dynamic and kinematic viscosity of ethylene, C2H4, also called ethene or acetene, at varying temperature and pressure - Imperial and SI Units.
Chemical, physical and thermal properties of ethylene, also called ethene, acetene and olefiant gas. Phase diagram included.
Absolute (dynamic) viscosity for common food products.
Absolute (dynamic) viscosities of some common gases.
The Hazen-Williams equation can be used to calculate the pressure drop (psi) or friction loss in pipes or tubes.
Thermodynamic properties of heavy water (D2O) like density, melting temperature, boiling temperature, latent heat of fusion, latent heat of evaporation, critical temperature and more.
ISO-VG viscosity grades for industrial lubricants.
International standard atmosphere in elevation -2000 to 30000 metre - pressure, temperature, density, viscosity, thermal conductivity and velocity of sound.
Viscosities and densities of ISO - and equivalent SAE grade oils.
Convert between Centistokes, Saybolt and Redwood seconds.
Convert between kinematic viscosity units like centistokes, poise, lentor and more.
Absolute (dynamic) viscosity values for some common fluids.
Kinematic viscosities of some common liquids like motor oil, diesel fuel, peanut oil and many more.
Online calculator, figures and tables showing dynamic and kinematic viscosity of methane, CH4, at varying temperature and pressure - Imperial and SI Units.
Figures and table showing changes in Prandtl number for methane with changes in temperature and pressure.
Online calculator, figures and tables showing dynamic and kinematic viscosity of liquid methanol,CH3OH, at varying temperature - Imperial and SI Units.
Dynamic viscosities for motor oils SAE 10 to 50 for temperatures ranging 0-100 oC.
Figures and tables showing Prandtl number of nitrogen at varying temperarure and pressure, SI and Imperial units.
Viscosities of fuel oils vs. temperature.
Pressure drop in oil pipes - viscosities ranging 100 - 600 Saybolt Universal Seconds.
Convert between commonly used oil viscosity units.
Online calculator, figures and tables showing dynamic and kinematic viscosity of oxygen, O2, at varying temperature and pressure - Imperial and SI Units.
Heat emission from steam or water heating pipes submerged in oil or fat - forced and natural circulation.
Calculate the volume flow discharged through a smooth-walled circular pipe.
Online calculators, figures and tables showing dynamic and kinematic viscosity of liquid and gaseous propane at varying temperarure and pressure, SI and Imperial units.
Figures and tables with Prandtl Number of liquid and gaseous propane at varying temperarure and pressure, SI and Imperial units.
Introduction and definition of the dimensionless Reynolds Number - online calculators.
Viscosities and densities of SAE Grade oils.
Seawater properties like density, saturation pressure, specific heat, electrical conductivity and absolute viscosity.
Comparing properties like specific gravity, freezing points and viscosity for secondary coolants like calcium chloride, sodium chloride, ethylene glycol and propylene glycol.
Absolute viscosity of steam at pressure ranging 1 - 10000 psia.
Friction loss in schedule 40 steel pipe with viscous liquids - viscosities ranging from water to oil.
Dynamic viscosities of sucrose water solutions vs. temperature.
Convert between viscosity units like Centiposes, milliPascal, CentiStokes and SSU.
Friction loss in steel pipes for fluids with viscosities ranging 32 - 80000 SSU.
Recommended max. flow velocities on delivery sides of pumps in viscous systems.
Recommended max. pump suction flow velocity for viscous fluids.
Absolute viscosity for water in centipoises for temperatures between 32 - 200oF.
Free online calculator - figures and tables with viscosity of water at temperatures ranging 0 to 360°C (32 to 675°F) - Imperial and SI Units.
Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!
We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.
Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.