What is the unit of measurement of Viscosity ?

DYNAMIC VISUALITY

1. Poise (Symbol: P) + centiPoise (Symbol: cP)

Named after French physician Jean Louis Marie Poiseuille (1799 – 1869), this is the CGS unit of viscosity, equivalent to dyne-seconds per square centimeter. It is the viscosity of a fluid where a tangential force of 1 dyne per square centimeter maintains a velocity difference of 1 centimeter per second between two parallel planes 1 centimeter apart.

Even when dealing with highly viscous liquids, this unit is most commonly the centipoise (cP), which is 0.01 Poise. Many everyday fluids with viscosities from 0.5 to 1000 cP.

2. Pascal-second (Symbol: Pa.s) + milliPascal-second (Symbol: mPa.s)

This is the SI unit of viscosity, equivalent to newton-seconds per square meter (N·sm–2). It is sometimes called Poiseuille (symbol Pl).

One Poise is exactly 0.1 Pa·s. One Poiseuille is equal to 10 Poise or 1000 cP, while 1 cP = 1 mPa·s (one millipascal-second).

KINEMATIC VISUALITY

1. Stokes (symbol: St) + centiStokes (symbol: cSt)

This is the CGS unit, which is equivalent to square centimeters per second (cm2 s–1). One Stokes is the ready-made viscosity divided by the density of the liquid in grams per cubic centimeter (g·cm–3). It is most commonly encountered as centistokes (cSt), equal to 0.01 times Stokes.

2. Saybolt Seconds Universal (symbol: SSU)

This is the time for 60 milliliters (ml) of liquid to flow through the calibration hole of the Saybolt Universal viscometer at the specified temperature, as specified by test method ASTM D 88. For higher viscosity, SSF(Saybolt Seconds Furol) is used. “Furol” comes from “fuel and road oil”.

3. Degree Engler

This is the ratio of the flow time of 200 ml of liquid to the flow time of 200 ml of water at the same temperature in a standard Engler viscometer.