1. A computer-performed method for calculating a transient current magnitude in a metal layer of an integrated circuit, said method comprising: selecting an interconnect path segment of said metal layer; obtaining circuit moments for nodes corresponding to endpoints of said segment; specifying an input voltage waveshape; computing current moments from said circuit moments and said waveshape; calculating a current value for said segment from at least one of said current moments; and storing the current calculated current value for the segment in a memory of a computer system.