Smithfield is located in Johnston county North carolina with a geographic area of 12.0 square miles. The total population in Smithfield is 12,697 with 48.2% male and 51.8% female. Children under age 5 represent 5.5% of the population, under age 18 equal 23.0% of the population and over age 65 is 18.9% of the population. The median household income is $34,077, per capita income is $23,774. There are a total of 5,015 housing units with 56.0% owner occupied. Education includes 24.9% of residents that are high school graduates and 28.0% with a bachelor's degree or higher. The average temperature in Smithfield in the summer is 75 degrees, and in the winter 38 degrees.