Viscosity Definitions and Conversions

Absolute Viscosity: is the force required to move a unit plane surface over another plane surface at unit velocity when surfaces are separated by a layer of fluid of unit thickness.

Unit of Absolute Viscosity in the metric system: poise and centipose
1 poise = 1 gram/(cm)(sec) and
1 centipoise = 1/100 poise

Unit of Absolute Viscosity in the English system: slugs/(ft)(sec)
1 slug/(ft)(sec) = 1/0.002089 poise

Kinematic Viscosity: is the absolute viscosity divided by density.

Unit of Kinematic Viscosity in the metric system and commonly used in the countries using the English system.

    stoke and centistoke
    1 stoke = 1 poise/density gm/ml)
    1 centistoke = 1/100 stoke

Other units of Kinematic Viscosity in the English system, the most practical unit for making
calculations is sq. ft./sec.; 1 sq. ft./sec. = 92903 centistoke and 1 centistoke = 1.0760 x 10E-5 sq. ft./sec.

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