The flow rates of gases at room temperature through various porous materials have been measured for large ranges of average pressure and pressure difference across the samples such that PΔP for a given sample varies by factors as large as 106. These rates are proportional to (PΔP)γ where γ decreases from 1 to 0.5 as the flow increases and 7 for a given medium is a function of an effective Reynolds number only, independent of the gas used. All the data, including those for transition flow, may be expressed by the following equation: where F is an average flow rate of gas passing through the medium measured in units of cm3/sec at 1 atm pressure, the coefficients c1 and c2 depend only on the properties of the porous medium and can be determined from experiments at low rates of laminar flow and high rates of fully turbulent flow, respectively, the coefficient α is given by ln 2, where ρ1 is the gas density at 1 atm pressure and room temperature, and η is the viscosity. Making the transformation and changing to the exponential base 2, the general equation becomes This dimensionless equation egresses experimental data for a variety of gases and porous media as examined in this study over a range of about 1011 for the variable x and about 2 × 109 for the variable y. It also egresses some data of others on flow through various porous metals and through beds of granular solids. Mean hydraulic radii of pores, effective numbers of pores, friction factors, and surface-roughness factors for the samples investigated are given.