Gainesville is located in Prince william county Virginia with a geographic area of 10.1 square miles. The total population in Gainesville is 16,391 with 49.3% male and 50.7% female. Children under age 5 represent 8.8% of the population, under age 18 equal 30.5% of the population and over age 65 is 9.1% of the population. The median household income is $143,490, per capita income is $47,033. There are a total of 4,928 housing units with 84.4% owner occupied. Education includes 11.2% of residents that are high school graduates and 59.5% with a bachelor's degree or higher. The average temperature in Gainesville in the summer is 71 degrees, and in the winter 35 degrees.