|Unit system||Centimetre–gram–second system of units|
|Unit of||Dynamic viscosity|
|Named after||Jean Léonard Marie Poiseuille|
|Derivation||1 P = 1 dyn⋅s/cm2|
|1 P in ...||... is equal to ...|
|CGS base units||1 cm−1⋅g⋅s−1|
|SI units||0.1 Pa⋅s|
The poise (symbol P; /pɔɪz, pwɑːz/) is the unit of dynamic viscosity (absolute viscosity) in the centimetre–gram–second system of units (CGS). 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 , that is, .
The analogous unit in the International System of Units is the pascal-second (Pa⋅s):
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. 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).
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).