Jacksonville, Florida is 5.5 times larger than Las Vegas.
Area: 1,988 km2 calculated
Jacksonville is the largest city in the U.S. state of Florida by population and the largest city by area in the contiguous United States. It is the county seat of Duval County, with which the city government consolidated in 1968. Wikipedia
Area: 363 km2 calculated
Las Vegas, officially the City of Las Vegas and often known as simply Vegas, is the most populous city in the state of Nevada and the county seat of Clark County. Wikipedia