Graphene-based materials are very interesting due to their excellent chemical, physical and mechanical properties, which make them extremely useful as preferred materials in various industrial applications. Liquid-phase exfoliation of graphite makes it possible to obtain graphene with a low level of defects. Many researchers have determined the size of graphene plates obtained by liquid-phase exfoliation of graphite, but there are no studies that analyze the relationship between the shape of the particles of the original graphite and graphene plates. This article analyzes the results of studies of the shape and size of parts of the original graphite and graphene plates. It was found that the shape of the initial graphite particles can be represented as an ellipsoid with different values of the semiaxes in three mutually perpendicular directions (length, width, thickness). Approximate ratios of these dimensions have been found, which can be used in calculating the process of liquid-phase exfoliation of graphite.