The attainable values of molecular-weight distribution (MWD) specified by die degree of polymerization and the polydispersity ill a batch free-radical polymerization reactor are described. The two-step method based on the quadratic profile of die instantaneous degree of polymerization is used to obtain die recipe producing the polymer with the desired MWD specification. The analytic solution for the quadratic profile is derived and analyzed in order to estimate the attainable MWD given the constraints on the range of the instantaneous degree of polymerization The entire computational procedure is intelligently organized, and thus die actual computational load is very low compared to the conventional optimization scheme. The MWD attainable under a specific operating condition with constraints in a batch styrene polymerization reactor is visualized and various reactor temperature trajectories that would produce the desired polymer product are calculated. The ability to predict the attainable MWD allows ail engineer to easily design the recipes that would meet the desired MWD specification.