| | Mechanicsville, VA | Bon Air, VA | United States |
| Population | 37,767 | 17,846 | 329,725,481 |
| Female Population | 51.1% | 52.9% | 50.5% |
| Male Population | 49.0% | 47.1% | 49.5% |
| Median Age | 41.7 | 42 | 38.4 |
| space3 | | | |
| Population - 2010 | 35,628 | 15,865 | 309,327,143 |
| Population - 2000 | 30,464 | 16,213 | 285,036,114 |
| Population - 1990 | 22,027 | 16,413 | 251,960,433 |
| Pop. 2000 to Now | 29.9% | 14.9% | 15.6% |
| Pop. 1990 to Now | 79.6% | 13.5% | 30.8% |
| space4 | | | |
| Population Density | 1,332.3 | 2,134.9 | 93.4 |
| Land Area | 28.3 | 8.4 | 3,531,905.4 |
| Water Area | 0.1 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Mechanicsville, VA | Bon Air, VA | United States |
| Age 0 to 4 | 5.3% | 5.6% | 5.9% |
| Age 5 to 9 | 5.2% | 5.5% | 6.1% |
| Age 10 to 14 | 7.8% | 6.2% | 6.6% |
| Age 15 to 17 | 4.5% | 5.0% | 3.9% |
| Age 18 to 20 | 4.4% | 4.4% | 4.0% |
| Age 21 to 24 | 3.3% | 3.8% | 5.2% |
| Age 25 to 34 | 10.8% | 10.3% | 13.8% |
| Age 35 to 44 | 12.4% | 14.9% | 12.9% |
| Age 45 to 54 | 12.8% | 14.1% | 12.6% |
| Age 55 to 59 | 7.4% | 7.2% | 6.7% |
| Age 60 to 64 | 7.2% | 5.5% | 6.3% |
| Age 65 to 74 | 10.3% | 10.0% | 9.6% |
| Age 75 to 84 | 5.6% | 4.4% | 4.5% |
| Age 85 and over | 3.0% | 3.2% | 1.9% |
| space1 | | | |
| Race | | | |
| | Mechanicsville, VA | Bon Air, VA | United States |
| White | 83.0% | 72.7% | 59.4% |
| Black | 8.5% | 12.1% | 12.2% |
| Asian | 1.6% | 3.9% | 5.6% |
| Native American | 0.1% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.0% | 0.2% |
| Other | 0.4% | 0.2% | 0.4% |
| Two or More Races | 4.6% | 3.2% | 3.2% |
| Hispanic | 1.8% | 7.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Mechanicsville, VA | Bon Air, VA | United States |
| Married Population | 53.2% | 52.4% | 49.8% |
| Currently Married | 51.1% | 50.9% | 48.0% |
| Married but Separated | 2.2% | 1.4% | 1.8% |
| Single Population | 46.8% | 47.6% | 50.2% |
| Never Married | 27.4% | 30.4% | 33.8% |
| Divorced | 12.1% | 10.8% | 10.8% |
| Widowed | 7.3% | 6.5% | 5.6% |
| space5 | | | |
| Household Size | 2.56 | 2.51 | 2.60 |
| Households | 14,675 | 6,959 | 124,010,992 |
| Family Households | 9,875 | 4,504 | 80,755,759 |
| Married couple, w/children | 30.1% | 37.6% | 30.5% |
| Married couple, no children | 46.5% | 43.7% | 42.9% |
| Non Family Households | 4,800 | 2,455 | 43,255,233 |
| Single householder, w/children | 14.4% | 10.4% | 15.8% |
| Single householder, no children | 8.9% | 8.3% | 10.8% |