The Boone County portion of Sheldahl is part of the Boone Micropolitan Statistical Area, while the Story County portion is part of the Ames Metropolitan Statistical Area. Together, these two areas form the Ames–Boone Combined Statistical Area. The small portion of the city that extends into Polk County is part of the Des Moines–West Des Moines Metropolitan Statistical Area.
According to the United States Census Bureau, the city has a total area of 0.8 square miles (2.2 km²), all of it land.
There were 129 households out of which 34.1% had children under the age of 18 living with them, 65.9% were married couples living together, 6.2% had a female householder with no husband present, and 22.5% were non-families. 18.6% of all households were made up of individuals and 9.3% had someone living alone who was 65 years of age or older. The average household size was 2.60 and the average family size was 2.96.
In the city the population was spread out with 26.2% under the age of 18, 6.5% from 18 to 24, 28.6% from 25 to 44, 25.6% from 45 to 64, and 13.1% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 103.6 males. For every 100 females age 18 and over, there were 105.0 males.
The median income for a household in the city was $48,393, and the median income for a family was $48,571. Males had a median income of $32,969 versus $25,000 for females. The per capita income for the city was $17,811. About 5.7% of families and 3.4% of the population were below the poverty line, including 2.0% of those under age 18 and none of those age 65 or over.