Monte Carlo simulations of polymer chains on a discretized lattice, where each atom occupies multiple lattice sites, have been shown to provide accuracies comparable with off-lattice simulations in one-tenth the computation time. For polyatomic molecules, the main requirement for the level of discretization required is set by the intramolecular geometry of the molecule. The current work provides a method to determine this level of discretization without running full off lattice simulations for comparison of results. Chains are generated off-lattice, placed on lattices of various discretizations, and the resulting errors are analyzed. We apply the method to three cases, united atom polyethylene, united atom polypropylene, and atomistic polyethylene. The atomic diameter to lattice size ratios required are 12 for the united atom cases, and 17 for atomistic polyethylene. (C) 2003 American Institute of Physics.