The present article aims to be a contribute for the development of a new methodological approach for public space dimensioning, including quantitative regulations and design guidelines. It starts from the point of view that the current way of designing public spaces is deeply marked by fragmented and individualized visions (and practices), that are unable to meet the extensive functional conflicts that today’s public space has to bear. Objectively, and based on a functional approach, it is proposed to develop a novel model for sizing the public space according to its expected usage loads. Despite the embryonic nature of the proposed model, the results show: the inadequacy of existing norms, because the territory matters!; and the potential to apply the developed model in several urban scenarios. The proposed model, for now only prospective, requires deepening and evaluation, thus pointing to future investigations.