A computer implemented method for calculating a ground capacitance adjust for a wire segment going through a given routing tile. The method includes providing the routing tile having a plurality of wires wherein the wire segment being a victim wire and neighboring wires being aggressor wires; computing ground capacitance adjusts for a victim wire averaged across all aggressor slew values and across possible spacing values between the victim wire and the neighboring aggressor wires to take into account a potential coupling effect by the neighboring aggressor wires, assuming a distribution of signal slews of wires belonging to the routing tile and assuming the victim wire's neighbors have signal slews from the distribution of slews for this tile for possible spacing values responsible for the coupling effect, to guide placement of the wire segment in the routing tile to avoid coupling noise.