This work presents a methodology for scaling up batch processes (BPs). First, the most popular scaleup methods differentiating batch from continuous processing are reviewed, revealing that traditional scaleup approaches do not consider BP characteristics and that many particular successful cases are reported, but no formal procedure has been developed for scaling up these processes. Considering these facts, a novel scaleup procedure is presented, in which a process phenomenological-based semiphysical model (PBSM) and its Hankel matrix are used for computing the state impactability index (SII) that allow the designer to determine (i) the main process dynamics at each stage of the batch and (ii) the critical point of the operating trajectory (OT) at which the batch must be scaled up. Finally, the methodology is applied to a batch suspension polymerization reactor, comparing the scaled unit design using this approximation and a traditional method.