<P> The Roman Empire was among the most powerful economic , cultural , political and military forces in the world of its time . It was one of the largest empires in world history . At its height under Trajan , it covered 5 million square kilometres . It held sway over an estimated 70 million people , at that time 21 % of the world 's entire population . The longevity and vast extent of the empire ensured the lasting influence of Latin and Greek language , culture , religion , inventions , architecture , philosophy , law and forms of government on the empire 's descendants . Throughout the European medieval period , attempts were even made to establish successors to the Roman Empire , including the Empire of Romania , a Crusader state ; and the Holy Roman Empire . By means of European colonialism following the Renaissance , and their descendant states , Greco - Roman and Judaeo - Christian culture was exported on a worldwide scale , playing a crucial role in the development of the modern world . </P>
what was the population of the roman empire at its height
70 million