J_{cow}(s_w) = a  \ ( s_{wn} )^{-1 / \lambda}

where

 – normalised water saturation,

 – critical water saturation,

 – model parameters which are set for laboratory data on capillary pressure and/or on resistivity water saturation during SHF.

Model parameter  is related to the the size of the pore size distribution.

The most popular value is 2 but it can vary to smaller or higher values.