This thesis work deals with the study of different grain size distribution and to measure the darcian permeability of foundry sand. The permeability of foundry sand is conventionally measured using parameters in foundries and provides a permeability number (PN). This permeability number can be used as a relative value between different samples and will not provide the permeability in darcian units. In this thesis project, we can perform measurements using an experimental setup that is developed to measure the darcian permeability. The results will be used for modelling and understanding phenomenon such as how the grain size distribution affects the permeability values of different grain size distribution.