Abstract: A computer is programmed to perform lithography simulation at a number of locations in a transverse direction relative to a length of a feature of an IC design, to obtain simulated intensities at the locations. The computer is further programmed to determine constants of a predetermined formula that models a trend of the simulated intensities as a function of distance (in the transverse direction), by curve-fitting. The computer is also programmed to compute a value (“CD predictor”) based on the just-determined constants, the formula and a known threshold intensity for a given position along the feature's length. The just-described process, of lithography-simulation, followed by curve-fitting, followed by CD predictor computation, is repeatedly performed to obtain a number of CD predictors at a corresponding number of positions along the feature's length. The CD predictors are used to identify a position of a critical dimension, for use in, for example, layout verification.