The input slew at a selected gate of an integrated circuit design is computed by assigning a default slew rate to the output gate of a previous logic stage which is greater than a median slew rate for the design. This default slew rate is propagated through the logic stage to generate an input slew rate at the selected gate. The default slew rate corresponds to a predetermined percentile applied to a limited sample of preliminary slew rates for randomly selected gates in the design. The default slew rate is adjusted as a function of known characteristics of the wirelength from the output gate to a first gate in the second logic stage. The delay of the selected gate is calculated based on the input slew rate. The input slew rate can be stored during one optimization iteration and used as a default slew rate during a later optimization iteration.