Pore diameters of zeolites are calculated using a new freely available software tool which identifies rings based on the crystallographic notation of atoms. In addition, an automated algorithm allows to extract information from molecular dynamics outputs so that dynamic pore diameters are calculated and compared to an experimental reference. This is useful in order to identify different rings along a given channel as well as for the calculation and analysis of ring deformations due to framework dynamics and sorbate diffusion.