Graphene shows unique electron-transport properties owing to the density of its carriers near the Dirac point. The quantum capacitance (CQ) of graphene is an intrinsic property that has been investigated theoretically in many previous studies. However, the development of CQ theory is hindered by the limited availability of related experimental works. In this perspective, experimental works on the CQ of mechanically exfoliated graphene, graphene synthesized by chemical vapor deposition (CVD), and graphene mesosponge are briefly summarized. The impact of structural properties such as stacking layers, defects, and nitrogen doping on CQ was experimentally investigated. Furthermore, the applicability of CQ theory was extended to three-dimensional graphene frameworks. Future research on CVD-synthesized and three-dimensional graphene is expected to enhance our comprehension of the underlying nature of CQ.