This study aims to characterise the urban dining rooms located in the province of Lusitania from a metrological and morphological point of view. The studied examples were identified in the cities of Conimbriga (Condeixa-a-Velha), Capera (Cáparra), Augusta Emerita (Mérida), and Mirobriga (Santiago do Cacém) and were built between the 1st and the 3rd century CE. The conducted analyses demonstrated the existence of a certain hierarchy in room dimensions, with widths being more homogeneous. This led to the definition of four size clusters, that have a more heterogeneous set of lengths associated, suggesting greater importance of room width, possibly related to the placement of the couches. The existence of relatively standardised size clusters, as well as the presence of several dining rooms in the same house, suggest a relationship between size and functional character, as well as the existence of established rules for the sizing of certain spaces.