Laboratory drop weight tests rig and numerical modelling have been used to investigate theimpact energy effect on the degree of dynamic fragmentation of cylindrical rock samples. Thedrop weight tests indicated that the degree of dynamic fragmentation of the Daley Dalesandstone formed a non-linear relation with impact energy. In the numerical modelling of thedrop weight test, the shear localisation developed in the Daley Dale sandstone was assumed torepresent discrete fracture planes. Shear bands, outputs of the image analysis of the numericalmodel, were used to separate solid material from shattered or broken material, allowing theFLAC output from the dynamic modelling to be processed into black and white fragmentedimages. This was undertaken to determine particle size distributions. Corresponding gradingcurves from the numerical modelling were then validated against the laboratory derived curvesindicating the potential of numerical modelling to simulate the process of rock fragmentation.