It is valuable to set an ideotype plant structure (i.e., ideal numbers and arrangement of sucrose sources, sinks, and pathways that maximize crop yield) as a goal for breeding with modern and near-future technologies. However, it is not easy to theoretically specify an ideotype because multiple factors need to be considered simultaneously. Here a method to obtain plant ideotypes using a simple mathematical model is described. The model identifies plant structures with maximal yield through a series of simulations of the dynamic changes in sucrose concentration at different positions of the plant. Originally developed for rice, this revised method can be applied to a wide range of crop plants.