Chicago is 4.1 times larger than Dayton, Ohio.
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
Area: 149 km2 calculated
Dayton is the sixth largest city in the U.S. state of Ohio and is the county seat of Montgomery County. Wikipedia