| poise | |
| Standard: | Centimetre–gram–second system of units |
| Quantity: | Dynamic viscosity |
| Symbol: | P |
| Namedafter: | Jean Léonard Marie Poiseuille |
| Extralabel: | Derivation |
| Extradata: | 1 P = 1 dyn⋅s/cm2 |
| Units1: | CGS base units |
| Inunits1: | 1 cm−1⋅g⋅s−1 |
| Units2: | SI units |
| Inunits2: | 0.1 Pa⋅s |
The poise (symbol P;) is the unit of dynamic viscosity (absolute viscosity) in the centimetre–gram–second system of units (CGS).[1] It is named after Jean Léonard Marie Poiseuille (see Hagen–Poiseuille equation). The centipoise (1 cP = 0.01 P) is more commonly used than the poise itself.
Dynamic viscosity has dimensions of
force x time/area
[M1L-1T-1]
The analogous unit in the International System of Units is the pascal-second (Pa⋅s):[2]
The poise is often used with the metric prefix centi- because the viscosity of water at 20 °C (standard conditions for temperature and pressure) is almost exactly 1 centipoise.[3] A centipoise is one hundredth of a poise, or one millipascal-second (mPa⋅s) in SI units (1 cP = 10−3 Pa⋅s = 1 mPa⋅s).[4]
The CGS symbol for the centipoise is cP. The abbreviations cps, cp, and cPs are sometimes seen.
Liquid water has a viscosity of 0.00890 P at 25 °C at a pressure of 1 atmosphere (0.00890 P = 0.890 cP = 0.890 mPa⋅s).[5]