| | Cary, NC | Alexandria, VA | United States |
| Population | 171,603 | 158,185 | 329,725,481 |
| Female Population | 50.6% | 51.6% | 50.5% |
| Male Population | 49.4% | 48.4% | 49.5% |
| Median Age | 39.1 | 37.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 137,116 | 140,737 | 309,327,143 |
| Population - 2000 | 94,536 | 128,283 | 285,036,114 |
| Population - 1990 | 43,858 | 111,183 | 251,960,433 |
| Pop. 2000 to Now | 83.6% | 23.7% | 15.6% |
| Pop. 1990 to Now | 295.8% | 42.8% | 30.8% |
| space4 | | | |
| Population Density | 2,995.2 | 10,593.0 | 93.4 |
| Land Area | 57.3 | 14.9 | 3,531,905.4 |
| Water Area | 1.1 | 0.4 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Cary, NC | Alexandria, VA | United States |
| Age 0 to 4 | 5.5% | 7.0% | 5.9% |
| Age 5 to 9 | 7.3% | 4.7% | 6.1% |
| Age 10 to 14 | 7.9% | 4.3% | 6.6% |
| Age 15 to 17 | 4.7% | 2.4% | 3.9% |
| Age 18 to 20 | 2.8% | 1.9% | 4.0% |
| Age 21 to 24 | 4.0% | 3.9% | 5.2% |
| Age 25 to 34 | 11.6% | 20.7% | 13.8% |
| Age 35 to 44 | 15.6% | 18.7% | 12.9% |
| Age 45 to 54 | 15.7% | 13.5% | 12.6% |
| Age 55 to 59 | 6.5% | 5.9% | 6.7% |
| Age 60 to 64 | 5.8% | 5.2% | 6.3% |
| Age 65 to 74 | 7.7% | 7.4% | 9.6% |
| Age 75 to 84 | 3.6% | 3.0% | 4.5% |
| Age 85 and over | 1.1% | 1.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | Cary, NC | Alexandria, VA | United States |
| White | 59.6% | 51.5% | 59.4% |
| Black | 7.7% | 21.1% | 12.2% |
| Asian | 20.2% | 6.4% | 5.6% |
| Native American | 0.2% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.6% | 0.3% | 0.4% |
| Two or More Races | 3.4% | 4.1% | 3.2% |
| Hispanic | 8.3% | 16.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Cary, NC | Alexandria, VA | United States |
| Married Population | 62.5% | 45.4% | 49.8% |
| Currently Married | 60.7% | 43.2% | 48.0% |
| Married but Separated | 1.8% | 2.2% | 1.8% |
| Single Population | 37.5% | 54.6% | 50.2% |
| Never Married | 25.7% | 40.2% | 33.8% |
| Divorced | 8.0% | 10.5% | 10.8% |
| Widowed | 3.8% | 3.9% | 5.6% |
| space5 | | | |
| Household Size | 2.66 | 2.11 | 2.60 |
| Households | 64,512 | 74,224 | 124,010,992 |
| Family Households | 46,511 | 34,516 | 80,755,759 |
| Married couple, w/children | 42.4% | 31.5% | 30.5% |
| Married couple, no children | 41.9% | 44.4% | 42.9% |
| Non Family Households | 18,001 | 39,708 | 43,255,233 |
| Single householder, w/children | 10.4% | 13.6% | 15.8% |
| Single householder, no children | 5.3% | 10.6% | 10.8% |