Chicago is 3.4 times larger than Brooklyn (NYC borough).
Area: 180 km2 calculated
Brooklyn is the most populous of New York City's five boroughs, with about 2.6 million people, as well as the second-largest in area. Wikipedia
Area: 608 km2 calculated
Chicago is the third most populous city in the United States, after New York City and Los Angeles. With 2.7 million residents, it is the most populous city in both the U.S. state of Illinois and the American Midwest. Wikipedia