In this paper we show that it is necessary to utilize different partitioning coefficients in interconnection length analyses which are based on Rent's rule, depending on whether one- or two-dimensional placement strategies are used. β, the partitioning coefficient in the power-law relationship αΒβ, provides a measure of the number of interconnections which cross a boundary enclosing Β blocks. The partitioning coefficients are β=p/2 and β=p for two- and one-dimensional arrays, respectively, where p is the experimental coefficient of the Rent relationship T=αΒp. Based on these separate partitioning coefficients, an average interconnection length prediction is presented for rectangular arrays that outperforms existing predictions. Examples are given to support this theory.