Laboratory and numerical cratering experiments into sandstone and quartzite targets were carried out under conditions ranging from pure strength– to pure gravity–dominated crater formation. Numerical models were used to expand the process of crater formation beyond the strength-dominated laboratory impact experiments up to the gravity regime. We focused on the effect of strength and porosity on crater size and determined scaling parameters for two cohesive materials, sandstone and quartzite, over a range of crater sizes from the laboratory scale to large terrestrial craters. Crater volumes and diameters of experimental and modeling data were measured, and scaling laws were then used to determine μ values for these data in the strength and gravity regimes. These μ values range between 0.48 and 0.55 for sandstone and between 0.49 and 0.64 for quartzite. The scaled crater dimensions in numerical models agree quite well with experimental observations. An accurate definition of the strength parameter in pi-group scaling is crucial for predicting the crater size, in particular, in the transitional regime from strength to gravity scaling. We determined an effective strength value that accounts for the weakening of target material due to the accumulation of damage. Using the numerical models, we found an effective strength of 4.6 kPa for quartzite and 3.2 kPa for sandstone, which are almost five orders smaller than the quasi-static experimental strength values that only account for the intact state of the target material.