dynamic viscosity
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 in which 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 for highly viscous fluids, this unit is often used as centipoise (cP), which is 0.01 poise. Many everyday fluids have viscosities between 0.5 and 1000 cP.
| Some typical dynamic viscosities (cP at 20°C) | |||
| Air | 0.02 | Oil SAE 20 | 125 |
| acetone | 0.3 | Oil SAE 50 | 540 |
| Methanol | 0.6 | castor oil | 986 |
| water | 1 | glycerin | 1490 |
| ethanol | 1.2 | pancake syrup | 2500 |
| HG | 1.5 | Maple sugar | 3200 |
| Linseed oil (raw material) | 28 | syrup | 20,000 |
| Corn oil | 72 | peanut butter | 250,000 |
| olive oil | 84 | window putty | 100,000,000 |
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. 1 poise equals 10 poises or 1000 cP, and 1 cP = 1 mPa·s (one milliPascal second).
| dynamic viscosity | the symbol | cP equivalent | ||
| 1 kilogram-force-second per square meter | kgf·s m-2 | 9 806.6501248 | ||
| 1 pound second per square foot | pdl s ft-2 | 1 488.164435 | ||
| 1 pound per foot per hour | lb (ft.h)-1 | 0.413379 | ||
| 1 pound per foot per second | lb(ft.s)-1 | 1 488.1639328 | ||
| 1 pound force second per square foot | lbf·s ft-2 | 47 880.2595148 | ||
| 1 pound force second per square inch (reyn) | lbf·s in-2 | 6 894 757 | ||
| 1 bullet per foot per second | slug (ft·s)-1 | 47 880.25898 | ||
kinematic viscosity
Stokes (symbol: St) + centi-Stokes (symbol: cSt)
This is the CGS unit, equivalent to square centimeters per second (cm2 s–1). One Stokes is equal to the viscosity in poise divided by the fluid density in grams per cubic centimeter (g cm–3). It is usually expressed in centistokes (cSt) and is equal to 0.01 Stokes.
Saybolt Seconds Universal (SSU)
This is the time for 60 milliliters (ml) of fluid to flow through the calibrated orifice of a Saybolt Universal Viscometer at a specified temperature, as specified in Test Method ASTM D 88. For higher viscosities, SSF (Saybolt Seconds Furol) is used. "Furol" comes from "Fuel and Road Oil".
Engler viscosity
This is the ratio of the flow time of 200 ml of fluid to the flow time of 200 ml of water at the same temperature in a standard Engler viscometer.
| Equivalent table | ||||
| kinematic viscosity | the symbol | cSt equivalent | ||
| 1 square centimeter per second | cm2 s-1 | 100 | ||
| 1 square meter per second | m2 s-1 | 1 000 000 | ||
| 1 square foot per second | ft 2 sec-1 | 92 903.04 | ||
| 1 square inch per second | in2 s-1 | 645.16 | ||
