Viscosity Calculator
Viscosity is how thick a fluid is, or how strongly it resists flowing. Engineers use two versions: dynamic viscosity, and kinematic viscosity, which divides the first by density.
This page converts dynamic viscosity into kinematic viscosity.
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How it works
Kinematic viscosity equals dynamic viscosity divided by density. With dynamic viscosity in millipascal-seconds and density in kilograms per cubic metre, multiplying by 1,000 and dividing by the density gives square millimetres per second.
Both figures usually come with a stated temperature on a data sheet. Viscosity changes a lot as a fluid warms or cools, so use the figure for the temperature you care about.
Worked example
A fluid with a dynamic viscosity of 1 and a density of 998 has a kinematic viscosity of 1.
Questions
What is a typical value for water?
Water is close to 1 millipascal-second at room temperature, which works out to about 1 square millimetre per second. Check a source for the exact temperature.
Where do I find dynamic viscosity?
Oil and paint data sheets often list it, sometimes as centipoise. One centipoise equals one millipascal-second, so the number carries over directly.
Why does temperature matter so much?
Warm fluids flow more easily, so their viscosity drops. A figure only applies to the temperature it was measured at.
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