Coquille is bordered by the Coquille River which drains part of the Coastal Range into the Pacific Ocean at Bandon.
According to the United States Census Bureau, the city has a total area of 2.7 square miles (7.1 km²), of which, 2.7 square miles (7.0 km²) of it is land and 0.37% is water.
There were 1,686 households out of which 28.2% had children under the age of 18 living with them, 51.1% were married couples living together, 12.0% had a female householder with no husband present, and 33.0% were non-families. 28.1% of all households were made up of individuals and 14.8% had someone living alone who was 65 years of age or older. The average household size was 2.35 and the average family size was 2.83.
In the city the population was spread out with 22.9% under the age of 18, 7.4% from 18 to 24, 25.3% from 25 to 44, 24.1% from 45 to 64, and 20.1% who were 65 years of age or older. The median age was 42 years. For every 100 females there were 94.3 males. For every 100 females age 18 and over, there were 91.8 males.
The median income for a household in the city was $29,931, and the median income for a family was $35,144. Males had a median income of $34,583 versus $21,567 for females. The per capita income for the city was $14,619. About 7.6% of families and 10.6% of the population were below the poverty line, including 15.3% of those under age 18 and 6.1% of those age 65 or over.