| | Knightdale, NC | Smithfield, NC | United States |
| Population | 18,614 | 11,168 | 329,725,481 |
| Female Population | 53.0% | 52.4% | 50.5% |
| Male Population | 47.0% | 47.6% | 49.5% |
| Median Age | 36 | 45.5 | 38.4 |
| space3 | | | |
| Population - 2010 | 11,500 | 11,089 | 309,327,143 |
| Population - 2000 | 5,958 | 11,510 | 285,036,114 |
| Population - 1990 | 1,884 | 7,540 | 251,960,433 |
| Pop. 2000 to Now | 204.2% | 15.8% | 15.6% |
| Pop. 1990 to Now | 861.9% | 76.8% | 30.8% |
| space4 | | | |
| Population Density | 2,713.8 | 941.7 | 93.4 |
| Land Area | 6.9 | 11.9 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Knightdale, NC | Smithfield, NC | United States |
| Age 0 to 4 | 7.3% | 4.6% | 5.9% |
| Age 5 to 9 | 7.1% | 6.9% | 6.1% |
| Age 10 to 14 | 8.1% | 7.2% | 6.6% |
| Age 15 to 17 | 4.4% | 3.8% | 3.9% |
| Age 18 to 20 | 3.6% | 1.7% | 4.0% |
| Age 21 to 24 | 2.5% | 4.5% | 5.2% |
| Age 25 to 34 | 15.4% | 8.9% | 13.8% |
| Age 35 to 44 | 17.0% | 11.6% | 12.9% |
| Age 45 to 54 | 11.8% | 15.3% | 12.6% |
| Age 55 to 59 | 7.8% | 7.4% | 6.7% |
| Age 60 to 64 | 5.6% | 9.7% | 6.3% |
| Age 65 to 74 | 6.3% | 10.9% | 9.6% |
| Age 75 to 84 | 2.2% | 5.6% | 4.5% |
| Age 85 and over | 0.8% | 1.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Knightdale, NC | Smithfield, NC | United States |
| White | 33.6% | 55.8% | 59.4% |
| Black | 49.4% | 26.0% | 12.2% |
| Asian | 1.7% | 1.7% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.9% | 0.0% | 0.4% |
| Two or More Races | 4.5% | 1.2% | 3.2% |
| Hispanic | 9.9% | 15.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Knightdale, NC | Smithfield, NC | United States |
| Married Population | 53.5% | 45.5% | 49.8% |
| Currently Married | 50.6% | 40.3% | 48.0% |
| Married but Separated | 2.9% | 5.2% | 1.8% |
| Single Population | 46.5% | 54.5% | 50.2% |
| Never Married | 32.4% | 31.3% | 33.8% |
| Divorced | 9.3% | 15.3% | 10.8% |
| Widowed | 4.8% | 7.9% | 5.6% |
| space5 | | | |
| Household Size | 2.53 | 2.34 | 2.60 |
| Households | 7,322 | 4,513 | 124,010,992 |
| Family Households | 4,966 | 2,564 | 80,755,759 |
| Married couple, w/children | 38.1% | 27.2% | 30.5% |
| Married couple, no children | 33.1% | 38.5% | 42.9% |
| Non Family Households | 2,356 | 1,949 | 43,255,233 |
| Single householder, w/children | 16.2% | 21.2% | 15.8% |
| Single householder, no children | 12.6% | 13.1% | 10.8% |