Abstract Several empirical correlations were developed relating the inertial, sometimes called the non-Darcy flow, coefficient (β) to permeability, porosity and water saturation. The correlations were developed using 407 data points taken on 24 cores over confining stress which was varied from 1000 psi to 5000 psi. The permeability range investigated was from 0.00197 to 1230 md. Previously published work1 on proppants extend the correlation to 350,000 md with a coefficient of determination of 98%. Water saturation has a significant effect on the coefficient. Confining stress effects are accounted for in the porosity and permeability values which decrease at elevated stress.