According to the United States Census Bureau, the city has a total area of 2.3 square miles (6.1 km²), of which, 2.3 square miles (6.0 km²) of it is land and 0.1 square miles (0.1 km²) of it (2.13%) is water.
There were 830 households out of which 32.2% had children under the age of 18 living with them, 52.8% were married couples living together, 9.8% had a female householder with no husband present, and 32.8% were non-families. 28.1% of all households were made up of individuals and 14.7% had someone living alone who was 65 years of age or older. The average household size was 2.41 and the average family size was 2.94.
In the city the population was spread out with 24.7% under the age of 18, 7.0% from 18 to 24, 27.6% from 25 to 44, 21.6% from 45 to 64, and 19.1% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 93.5 males. For every 100 females age 18 and over, there were 90.0 males.
The median income for a household in the city was $40,223, and the median income for a family was $45,515. Males had a median income of $34,524 versus $22,438 for females. The per capita income for the city was $19,946. About 5.6% of families and 8.3% of the population were below the poverty line, including 15.4% of those under age 18 and 3.3% of those age 65 or over.
Farmer City is part of Blue Ridge Community Unit School District #18 sharing facilities with nearby Mansfield, Illinois. Farmer City facilities include the District Unit Office, the Ruth M. Schneider Elementary School (K-3) and Blue Ridge High School.
Farmer City is also well known for its vast and varied antique shops, most of which are located on Main Street.