Craters produced by projectile impact in granular materials were studied for a wide range of energies and projectile types. Crater sizes were shown to depend on projectile size and shape and on the particle size of the target material. The volume of the impact crater was related to the kinetic energy of the projectile and to the measurable cohesive strength of the target material. Excellent agreement was found between the experimental results and a hydrodynamic theory of cratering slightly modified from earlier studies.