A method for computing power consumption includes querying a software database for a key node and a gate comprising an input port, connected to the key node, and an output port. The software database is created from a net list associated with a design. The method includes calculating a probability of activity level at the output port based on a predetermined activity level at the key node, and querying the software database for next gate comprising a next input port, connected to the previous output port, and a next output port. The method includes calculating a probability of activity level at the next output port based on the probability of activity level at the previous output port. The method includes computing a sub-circuit gate power by sum of power of all the gates based on the probability of activity level at output ports of the gates.