# Poise (unit)

The poise (symbol P; /pɔɪz, pwɑːz/) is the unit of dynamic viscosity (absolute viscosity) in the centimetre–gram–second system of units. It is named after Jean Léonard Marie Poiseuille (see Hagen–Poiseuille equation).

poise
Unit systemCentimetre–gram–second system of units
Unit ofDynamic viscosity
SymbolP
Named afterJean Léonard Marie Poiseuille
Conversions
1 P in ...... is equal to ...
CGS base units   1 g⋅cm−1⋅s−1
SI units   0.1 Pa⋅s
$1~{\text{P}}=0.1~{\text{kg}}{\cdot }{\text{m}}^{-1}{\cdot }{\text{s}}^{-1}=1~{\text{g}}{\cdot }{\text{cm}}^{-1}{\cdot }{\text{s}}^{-1}=1~{\text{dyn}}{\cdot }{\text{s}}{\cdot }{\text{cm}}^{-2}.$ The analogous unit in the International System of Units is the pascal-second (Pa⋅s):

$1~{\text{Pa}}{\cdot }{\text{s}}=1~{\text{N}}{\cdot }{\text{s}}{\cdot }{\text{m}}^{-2}=1~{\text{kg}}{\cdot }{\text{m}}^{-1}{\cdot }{\text{s}}^{-1}=10~{\text{P}}.$ The poise is often used with the metric prefix centi- because the viscosity of water at 20 °C (NTP) 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).