The total surface area of particles per unit volume of rock, or the internal surface area of total pores per unit volume of rock, is called the specific surface area of the rock. The finer the rock particles, the smaller the pore channels formed, and the greater the resistance encountered by a certain amount of air passing through the rock sample, resulting in a larger measured specific surface area; On the contrary, the smaller the aspect ratio.

The size of the rock specific surface is related to other physical properties of the rock, such as permeability, porosity, adsorption capacity, etc., especially with porosity and permeability. The equipment calculates the specific surface of the rock by measuring the pressure difference H and corresponding flow rate Q passing through the core.