How this calculator works
The IAPWS 2008 viscosity equation combines dilute-gas and finite-density terms. The density input comes from the IAPWS 1992 saturated-liquid density relation. Critical enhancement is omitted far below the critical temperature. These values describe pure liquid water on the saturation curve from approximately 0 to 100 C; the 0 C endpoint is a tiny extension below the triple point. Near room temperature they closely approximate ordinary low-pressure water, but they are not high-pressure or salt-water properties. A table shows the temperature trend.
Formula
mu = mu_reference mu0(T/647.096) mu1(T/647.096,rho/322), with mu_reference = 1 micropascal second. nu = mu/rho; cP = 1000 mu_Pa_s; cSt = 1000000 nu_m2_s.
Worked example
At 20 C the model gives about 998.16 kg/m3 density and 1.0016 mPa s dynamic viscosity. Near 100 C viscosity falls to about 0.2816 mPa s.
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Frequently asked questions
Are cP and mPa s equal?
Yes. One centipoise equals one millipascal second.
Why is kinematic viscosity a different quantity?
It divides dynamic viscosity by density and has units of area per time.
Does this cover steam?
No. This page restricts the calculation to the saturated liquid branch between 0 and 100 C.