Poise (unit)

poise
Unit system	Centimetre–gram–second system of units
Unit of	Dynamic viscosity
Symbol	P
Named after	Jean Léonard Marie Poiseuille
Derivation	1 P = 1 dyn⋅s/cm2
Unit conversions
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. 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 dimension $\mathrm{force \times time/area}$.

Failed to parse (Missing <code>texvc</code> executable. Please see math/README to configure.): {\displaystyle 1~\text{P} = 0.1~\text{m}^{-1} {\cdot} \text{kg} {\cdot} \text{s}^{-1} = 1~\text{cm}^{-1} {\cdot} \text{g} {\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):

Failed to parse (Missing <code>texvc</code> executable. Please see math/README to configure.): {\displaystyle 1~\text{Pa} {\cdot} \text{s} = 1~\text{N} {\cdot} \text{s} {\cdot} \text{m}^{-2} = 1~\text{m}^{-1} {\cdot} \text{kg} {\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).

See also

• Poiseuille
• Viscosity