Structured ASICs present an attractive alternative to reducing de-sign costs and turnaround times in nanometer designs. As with conven-tional ASICs, such designs require global wires to be buffered. However, via-programmable designs must prefabricate and preplace buffers in the layout. This oaper proposes a novel and accurate statistical estimation technique jo. distributing prefabricated buffers through a layout. It employs Rent's rule to estimate the buffer distribution required for the layout, so that an appropriate structured ASIC may be selected for the design. Experimental results show that the estimation for a uniform buffer distribution is accurate and economic.