Abstract: An innovative method and system for calculating realistic current and power of a circuit prior to silicon utilizes simulation and test vectors to determine a number of variables to accurately perform current calculations close to actual silicon results. Input test vectors which preferably are similar in function to applications utilized with the circuit are used to drive a model of the circuit. The simulator operating the model maintains the toggle count for each device of the circuit. A characterization table is generated which contains an average switching current value of a type of a device for different values of capacitive loads. Typically, this table is generated once and is used for a multiplicity of calculations. An activity factor can then be generated based on the number of the toggle count during a sample time period and the number of clock cycles during the sample period.