The present work has been undertaken with an objective to fill the gaps of previous studies and to explore guidelines to standardize the test specimen for evaluating formability with a single specimen in single point incremental forming (SPIF). Two candidate geometries for formability testing (i.e. varying wall angle pyramidal frustum and varying wall angle conical frustum) have been compared by varying geometrical parameters and materials. The critical size in horizontal plane (i.e. half-side length/curvature radius) and critical initial forming angle have been identified and compared for the two geometries. The critical size in horizontal plane has been found to be different for the two geometries. The critical initial forming angle has been found to be same for the two geometries. For various sheet materials, the difference in the formability of VWACF and VWAPF shows a dependence upon the percent reduction in area at tensile fracture.