Much still remains uncertain and controversial about the mechanophysical parameters involved in graphite exfoliation. Here, we quantify the expansion characteristics of natural graphite in the microwave-irradiated exfoliation where KMnO4 and HNO3 are used as an oxidant and an intercalant, respectively. As a mark of the degree to which graphite becomes exfoliated, the expansion ratio of graphite is investigated as a function of mix ratio by weight of 3 ingredients (i.e., graphite, KMnO4, and HNO3), mixing time, and graphite physical properties. The findings of this study will lead to a better understanding of graphite exfoliation and make it possible to achieve the industrial-scale production of defect-free graphene.