Auburndale is located at (28.066969, -81.795252).
According to the United States Census Bureau, the city has a total area of 24.1 km² (9.3 mi²). 13.5 km² (5.2 mi²) of it is land and 10.6 km² (4.1 mi²) of it (43.87%) is water.
There were 4,119 households out of which 35.3% had children under the age of 18 living with them, 52.1% were married couples living together, 15.7% had a female householder with no husband present, and 27.1% were non-families. 21.7% of all households were made up of individuals and 9.8% had someone living alone who was 65 years of age or older. The average household size was 2.63 and the average family size was 3.02.
In the city the population was spread out with 27.2% under the age of 18, 9.0% from 18 to 24, 27.8% from 25 to 44, 20.8% from 45 to 64, and 15.3% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 92.2 males. For every 100 females age 18 and over, there were 89.6 males.
The median income for a household in the city was $34,184, and the median income for a family was $36,303. Males had a median income of $30,468 versus $21,232 for females. The per capita income for the city was $15,510. About 13.4% of families and 17.3% of the population were below the poverty line, including 28.3% of those under age 18 and 7.6% of those age 65 or over.