Molecular volcano plots, a tool generally used to identify ideal catalysts for a given chemical transformation, are employed in an alternative fashion to examine the substrate scope by revealing the range of substrates that can be accommodated by a single catalyst. Here the power to rationalize and better understand the substrate scope is demonstrated through the evaluation of the energetics of various electrophilic substrates for a Suzuki cross-coupling reaction. The plots reproduce experimentally known trends while quantifying the magnitude to which the overall activity depends on a substrate's intrinsic electronic and steric properties and how these energetics are altered by the addition of substituent groups or changes to the core structure. Overall, the information revealed by these substrate volcanoes can be used in tandem with conventional molecular volcano plots to identify general catalyst design principles for a series of substrates.