Centipoise

Centipoise (cP) is a unit of dynamic viscosity in the centimetre–gram–second (CGS) system. It is defined as one hundredth of a poise, with 1 poise equal to 0.1 Pa·s. Therefore 1 cP = 0.01 poise = 0.01 × 0.1 Pa·s = 0.001 Pa·s. In SI terms, 1 cP equals 1 millipascal-second (mPa·s), and 1 Pa·s equals 1,000 cP.

Dynamic viscosity measures a liquid’s resistance to shear and flow. It is typically reported in cP for liquids used in laboratories and industry. Viscosity is measured with viscometers, including rotational instruments such as Brookfield viscometers and capillary viscometers such as Cannon-Fenske. Temperature strongly affects viscosity: as temperature increases, viscosity generally decreases.

Typical values span a wide range. At room temperature, water is about 1 cP. Glycerol at around 20°C is roughly 1,000–1,500 cP. Vegetable oils often lie in the tens to hundreds of cP range, depending on temperature. Honey, syrups, and heavy molasses can have viscosities of thousands of cP.

Relationship to kinematic viscosity is established by ν = μ/ρ, where ν is kinematic viscosity, μ is dynamic viscosity, and ρ is density. In the CGS system, the unit for kinematic viscosity is the stoke (St), where 1 St = 100 cm2/s; 1 St corresponds to 100 cSt. Thus cP measures dynamic viscosity, while cSt measures kinematic viscosity, linked through fluid density.