A previously published pore scale model provides a simple analytic expression relating the permeability of a natural granular media to its porosity. This model is quantitatively accurate at high to intermediate porosities. It is based on two independent parameters, porosity and average grain size. At low porosities, however, the model is unable to capture the experimentally observed trends. Percolation provides a natural description of the pore closure evident in sedimentary media at low porosities. The use of percolation concepts provides the necessary input to predict the permeability in the porosity range where pore blocking occurs. Thus a simple analytic model, utilizing an experimental value for the percolation threshold, is derived for the permeability of sandstones and calcite aggregates over the full range of porosity. ¿ American Geophysical Union 1996