According to the United States Census Bureau, the town has a total area of 1.9 square miles (4.9 km2), of which, 1.9 square miles (4.9 km2) of it is land and 0.04 square miles (0.10 km2) of it (1.03%) is water.
There were 1,052 households out of which 34.0% had children under the age of 18 living with them, 50.1% were married couples living together, 7.4% had a female householder with no husband present, and 39.4% were non-families. 24.0% of all households were made up of individuals and 2.0% had someone living alone who was 65 years of age or older. The average household size was 2.55 and the average family size was 3.00.
In the town the population was spread out with 23.6% under the age of 18, 6.8% from 18 to 24, 42.3% from 25 to 44, 24.4% from 45 to 64, and 3.0% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 108.8 males. For every 100 females age 18 and over, there were 110.6 males.
The median income for a household in the town was $67,200, and the median income for a family was $73,375. Males had a median income of $40,791 versus $30,532 for females. The per capita income for the town was $30,746. About 4.9% of families and 6.3% of the population were below the poverty line, including 5.9% of those under age 18 and 6.8% of those age 65 or over.
Basalt is well known for its Gold Medal trout fishing in the Frying Pan River. Ruedi Reservoir is also a popular regional destination for boating and other watersports. Basalt is a hub for mountain biking in the Roaring Fork valley. There are a dozen world class cross country trails as well as lift-accessed downhilling within 15 miles of Basalt, both up and down the valley.