Contact holes (CHs) created by 193i lithography were shrunken by directed self-assembly of polystyrene-b-methylmethacrylate (PS-PMMA) block copolymers (BCPs). The placement error of these highly confined systems is determined both experimentally and by simulations. Good agreement between simulations (2 nm) and experiments was observed (2 nm). Extensive simulations show that the placement error is dependent on the length of the PS block only, indicating that the placement error is intrinsic to the BCP. This was explained by considering the BCPs as springs. For double CHs, a relation is found between the offset of the CH from the center of the CHs and the additional placement error.