With the increasing size and sophistication of circuits and specifically in the presence of IP blocks, new wirelength estimation methods are needed in the design flow of large-scale circuits. Up to now, the proposed techniques for wirelength estimation in the presence of IP blocks approached this problem either in a flat framework based on the geometrical structure of the circuit or in a hierarchical framework based on uniform distribution property for standard cells. In this paper, we propose a technique for hierarchical derivation of wirelength estimation in the presence of single and multiple blockages using Rent?s parameter of the circuit by assuming non-uniform probability distribution for standard cells. To measure the accuracy of our estimation, we compared our results with the results of placement and routing using a commercial CAD tool. The results illustrate that in the presence of multiple IP blocks, the average error of our technique is less than 8%, as compared to its counterparts with the average error of 35% and 150%.