This county is also a part of the Washington Metropolitan Area.
As of the census of 2005, there were 117,874 people, 38,237 households, and 24,481 families residing in the county. The population density was 342 people per square mile (132/km²). There were 31,405 housing units at an average density of 116 per square mile (45/km²). The racial makeup of the county was 79.00% white, 15.6% African American, 0.45% Native American, 2.1% Asian, 0.10% Pacific Islander, 1.21% from other races, and 2.47% from two or more races. 5.5% of the population were Hispanic or Latino of any race.
By 2005 Stafford County's population was 72.8% non-Hispanic whites. African-Americans were 16.1% of the total population. Native Americans were 0.4% of the county total. Asians 2.3%. Native Hawai'ians and other Pacific islanders 0.2%, thus making Stafford County one of the high percentage NHPI population counties in the country. Latinos were 6.4% of the population, above the percentage of Latinos in all of Virginia, put far below Stafford County's northern neighbors.
As of 2000 there were 38,187 households out of which 46.90% had children under the age of 18 living with them, 68.00% were married couples living together, 9.30% had a female householder with no husband present, and 18.90% were non-families. 13.80% of all households were made up of individuals and 3.40% had someone living alone who was 65 years of age or older. The average household size was 3.01 and the average family size was 3.32.
In the county, the population was spread out with 31.60% under the age of 18, 7.80% from 18 to 24, 33.70% from 25 to 44, 21.10% from 45 to 64, and 5.90% who were 65 years of age or older. The median age was 33 years. For every 100 females there were 101.10 males. For every 100 females age 18 and over, there were 99.50 males.
The median income for a household in the county was $75,546, and the median income for a family was $78,575 (these figures had risen to $85,793 and $95,433 respectively as of a 2007 estimate). Males had a median income of $47,080 versus $31,469 for females. The per capita income for the county was $24,762. About 2.40% of families and 3.50% of the population were below the poverty line, including 3.30% of those under age 18 and 5.30% of those age 65 or over.