In this paper, we have proposed a method to characterize various types of powder mixers based on the mechanical energy applied to the powders during the mixing operation using the soft dye granules (the agglomerates of fine Fe2O3 particles) as a stress-sensing material (SSM). The disintegration process of Fe2O3 agglomerates in the bulk CaCO3 powder was expressed by means of a simplified, comminution model and the fracture of agglomerates was dealt with as well as that of brittle materials. The energy required to disintegrate the Fe2O3 agglomerates was estimated in a high-speed agitating-type mixer and related to the mixing time. The disintegration energy in a bead mill agreed with the net applied energy estimated by using spherical copper particles as a SSM. It has been proved that the mechanical energy is quantitatively evaluated in various powder mixers. By using the change in the disintegration energy with the mixing time, i.e. the energy characteristic curve, the powder mixers can be characterized on the uniform scale of mechanical energy regardless of equipment structure and the principal mixing mechanism in each mixer can be clarified.