For many reactions, a pipe flow reactor and a cascade of ideally mixed reactors yield similar results, if we use a proper correlation between the Bodenstein number of the pipe flow reactor and the number of stages for the cascade. However, existing equations for this correlation, which are derived from residence time considerations, apply only for Bodenstein numbers greater than 7 or stage numbers greater than 6. In this paper a new equation is developed by comparing the governing equations for the reaction in both systems. It is shown that this correlation yields good agreement of the output concentrations for all stage numbers down to a single stage, respectively, zero Bodenstein number, even for a successive reaction.