As of the census of 2000, there are 500 people, 173 households, and 139 families residing in the town of Round Hill, Virginia. The population density is 919.3/km² (2,333.8/mi²). There are 177 housing units at an average density of 325.4 persons/km² (826.2 persons/mi²). The racial makeup of the town is 91.60% White, 7.20% African American, 0.00% Native American, 0.60% Asian, 0.00% Pacific Islander, 0.00% from other races, and 0.60% from two or more races. 1.40% of the population are Hispanic or Latino of any race.
There are 173 households out of which 42.2% have children under the age of 18 living with them, 65.3% are married couples living together, 12.1% have a woman whose husband does not live with her, and 19.1% are non-families. 15.6% of all households are made up of individuals and 4.6% have someone living alone who is 65 years of age or older. The average household size is 2.89 and the average family size is 3.22.
In the town the population is spread out with 31.4% under the age of 18, 4.8% from 18 to 24, 33.0% from 25 to 44, 23.0% from 45 to 64, and 7.8% who are 65 years of age or older. The median age is 36 years. For every 100 females there are 100.8 males. For every 100 females age 18 and over, there are 93.8 males.
The median income for a household in the town is $58,929, and the median income for a family is $62,361. Males have a median income of $41,375 versus $33,304 for females.
The per capita income for the town is $24,925. 5.4% of the population and 4.2% of families are below the poverty line. Out of the total people living in poverty, 3.5% are under the age of 18 and 15.7% are 65 or older.