Thin-film evaporator (TFE) is a popular continuous distillation/evaporation technology for pharmaceutical and fine chemical industries and has several equipment and process configurations that make fundamental modeling approaches very challenging. Specifically, moving wipers and lack of fluid dynamics and intraphase and interphase mixing knowledge contribute to the difficulty of developing predictive models. In this article, we present a novel, simple, and practical TFE model developed for active pharmaceutical ingredient continuous manufacturing. The model couples thermodynamic and countercurrent N-continuously stirred tank reactor models and is capable of predicting the TFE performance using various process parameters as inputs. The model's expanded usage is detailed for the case where the distillate-to-feed ratio was used to control the TFE.