A method of generating net routing constraints for nets of an IC design includes generating a file with hashes organized by nets. Each hash has attributes of a net, e.g. net name, length, fanout, total actual route (AR) resistance, a corresponding virtual route (VR) resistance, and a number of vias. A wire only AR resistance for each net can be calculated. Wire scaling factors can be calculated using the wire only AR resistances and their corresponding VR resistances. Wire scaling factors can be binned by one or more net characteristics. An average wire scaling factor can be calculated for each bin. Code used by a place and route tool can then be generated, wherein the code applies the average wire scaling factors to nets of the design to improve pre-route and post-route correlation.