Plainfield is located in Sullivan county New hampshire with a geographic area of 0.6 square miles. The total population in Plainfield is 265 with 49.8% male and 50.2% female. Children under age 5 represent 1.9% of the population, under age 18 equal 9.4% of the population and over age 65 is 20.8% of the population. The median household income is $87,895, per capita income is $52,229. There are a total of 134 housing units with 57.5% owner occupied. Education includes 51.5% of residents that are high school graduates and 41.8% with a bachelor's degree or higher. The average temperature in Plainfield in the summer is 68 degrees, and in the winter 23 degrees.