The effect of fracture specimen parameters like side grooving magnitude, its root radius and angle on the critical stretch zone width formation studied. It is found that there is maximum limit of side grooving magnitude and a minimum limit of root radius and angle which will provide geometry independent evaluation of critical SZW. It is concluded that side grooving magnitude should not be larger than 0.25 times thickness; root radius should not be less than 100. μm and the side grooving angle should not be less than 70°. © 2016 Elsevier Ltd.