A critical‐state calculation of the magnetization of hard type‐II superconducting grains having anisotropic critical‐current densities is given. The analysis shows how the critical‐current densities should be deduced from magnetization measurements for various grain morphologies. A universal curve of the magnetization hysteresis versus one of the grain dimensions is presented, showing that the hysteresis does not change linearly with grain size. Applications to single crystals and to bulk materials are made.