Gardner is located in Johnson county Kansas with a geographic area of 11.7 square miles. The total population in Gardner is 21,936 with 49.1% male and 50.9% female. Children under age 5 represent 8.7% of the population, under age 18 equal 30.0% of the population and over age 65 is 7.5% of the population. The median household income is $78,193, per capita income is $30,355. There are a total of 7,353 housing units with 65.0% owner occupied. Education includes 22.4% of residents that are high school graduates and 36.0% with a bachelor's degree or higher. The average temperature in Gardner in the summer is 76 degrees, and in the winter 32 degrees.