Durham, North Carolina is 4.1 times larger than Boulder, Colorado.
Area: 68 km2 calculated
Boulder is the county seat and most populous city of Boulder County and the 11th most populous city in the U.S. state of Colorado. Boulder is located at the base of the foothills of the Rocky Mountains at an elevation of 5,430 feet. The city is 25 miles northwest of Denver. Wikipedia
Area: 276 km2 calculated
Durham is a city in the U.S. state of North Carolina. It is the county seat of Durham County, though portions also extend into Wake County in the east and Orange County in the west. Wikipedia