The determination of the properties of porous solids remains an integral element to the understanding of adsorption, transport and reaction processes in new and novel materials. The advent of molecular simulation has led to an improved understanding and prediction of adsorption processes using molecular models. These molecular models have removed the constraints of traditional adsorption theories, which require rigid assumptions about the structure of a material. However, even if we possess a full molecular model of a solid, it is still desirable to define the properties of this solid in a standard manner with quantities such as the accessible volume, surface area and pore size distribution. This talk will present Monte Carlo integration methods for calculating these quantities in a physically meaningful and unambiguous way. The proposed methods for calculating the surface area and pore size distribution were tested on an array of idealised solid configurations including cylindrical and cubic pores. The method presented is adequate for all configurations tested giving confidence to its applicability to disordered solids. The method is further tested by using several different noble gas probe molecules. Finally, the results of this technique are compared against those obtained by applying the BET equation for a range of novel materials.