A computer-implemented method to generate a placement for a plurality of instances for an integrated circuit (IC) by utilizing a novel weighted-average (WA) wirelength model, which outperforms a well-known log-sum-exp wirelength model, to approximate the total wirelength. The placement is determined by performing an optimization process on an objective function which includes a wirelength function approximated by the WA wirelength model. The method can be extended to generate a placement for a plurality of instances for a three-dimensional (3D) integrated circuit (IC) which considers the sizes of through-silicon vias (TSVs) and the physical positions for TSV insertion. With the physical positions of TSVs determined during placement, 3D routing can easily be accomplished with better routed wirelength, TSV counts, and total silicon area.