On 31 December 2011, the city-state of Berlin had a population of 3.5 million registered inhabitants in an area of 891.82 km2 .The city's population density was 3,848 inhabitants per km². The urban area of Berlin stretches beyond the city limits and comprises about 3.7 million people, while the metropolitan area of the Berlin-Brandenburg region is home to about 4.5 million in an area of 5,370 km2 .
Berlin is the second most populous city proper and the ninth most populous urban area in the European Union.