According to the United States Census Bureau, the city has a total area of 9.3 square miles (24.0 km²), of which, 9.2 square miles (23.8 km²) of it is land and 0.1 square miles (0.2 km²) of it (0.97%) is water.
There were 3,864 households out of which 45.9% had children under the age of 18 living with them, 69.4% were married couples living together, 7.6% had a female householder with no husband present, and 19.8% were non-families. 16.1% of all households were made up of individuals and 5.3% had someone living alone who was 65 years of age or older. The average household size was 2.87 and the average family size was 3.23.
In the city the population was spread out with 32.6% under the age of 18, 5.6% from 18 to 24, 31.1% from 25 to 44, 23.1% from 45 to 64, and 7.6% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 100.7 males. For every 100 females age 18 and over, there were 95.5 males.
The median income for a household in the city was $65,313, and the median income for a family was $71,907. Males had a median income of $50,962 versus $29,066 for females. The per capita income for the city was $27,226. About 4.0% of families and 3.8% of the population were below the poverty line, including 4.9% of those under age 18 and 3.5% of those age 65 or over.
Eagle is a part of the Meridian School District and is home to one high school (Eagle High School), one alternative high school (Eagle Academy), one middle school (Eagle Middle School), and three elementary schools (Eagle Elementary School, Eagle Hills Elementary School, and Seven Oaks Elementary School). The latter of the three elementary schools provides a year-around option for students in grades K-5. There are also two charter schools (North Star Charter School, Rolling Hills Charter School) and one private arts school (ArtsWest School).
The 2008 NBC reality television show The Baby Borrowers was filmed in Eagle.