Three limestone powders, differing only in specific surface area, were agglomerated in a balling drum to form pellets of various sizes. The pellets were tested for dry compressive strength at different rates of deformation. A limiting elastic energy criterion for failure was used to derive the relation (analogous to the classical Hertz relation for strength of an elastic isotropic sphere) between the pellet size, the total deformation, and the load at failure. The surface area of the powder, the porosity of the pellet, and its compressive strength are analytically related; the results are in good agreement with the experimental data.