Despite the relatively short existence of the Carolingian Empire when compared to other European dynastic empires, its legacy far outlasts the state that had forged it. In historiographical terms, the Carolingian Empire is seen as the beginning of 'feudalism' or rather, the notion of feudalism held in the modern era. Though most historians would be naturally hesitant to assign Charles Martel and his descendants as founders of feudalism, it is obvious that a Carolingian 'template' lends to the structure of central medieval political culture.

The size of the empire at its inception was around 1,112,000 square kilometres (429,000 sq mi), with a population of between 10 and 20 million people. Its heartland was Francia, the land between the Loire and the Rhine, where the realm's primary royal residence, Aachen, was located. In the south it crossed the Pyrenees and bordered the Emirate of Córdoba and, after 824, the Kingdom of Pamplona to the north it bordered the kingdom of the Danes to the west it had a short land border with Brittany, which was later reduced to a tributary and to the east it had a long border with the Slavs and the Avars, who were eventually defeated and their land incorporated into the empire. In southern Italy, the Carolingians' claims to authority were disputed by the Byzantines (eastern Romans) and the vestiges of the Lombard kingdom in the Principality of Benevento. The term "Carolingian Empire" is a modern convention and was not used by its contemporaries.