| | Gardendale, AL | Carbon Hill, AL | United States |
| Population | 15,920 | 1,522 | 329,725,481 |
| Female Population | 52.5% | 52.0% | 50.5% |
| Male Population | 47.5% | 48.0% | 49.5% |
| Median Age | 40.5 | 40.4 | 38.4 |
| space3 | | | |
| Population - 2010 | 13,963 | 2,025 | 309,327,143 |
| Population - 2000 | 11,626 | 2,071 | 285,036,114 |
| Population - 1990 | 9,251 | 2,115 | 251,960,433 |
| Pop. 2000 to Now | 21.4% | -9.0% | 15.6% |
| Pop. 1990 to Now | 52.6% | -10.9% | 30.8% |
| space4 | | | |
| Population Density | 696.0 | 276.7 | 93.4 |
| Land Area | 22.9 | 5.5 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Gardendale, AL | Carbon Hill, AL | United States |
| Age 0 to 4 | 8.9% | 4.3% | 5.9% |
| Age 5 to 9 | 5.5% | 5.2% | 6.1% |
| Age 10 to 14 | 4.5% | 7.8% | 6.6% |
| Age 15 to 17 | 3.5% | 4.5% | 3.9% |
| Age 18 to 20 | 4.5% | 4.7% | 4.0% |
| Age 21 to 24 | 3.7% | 11.1% | 5.2% |
| Age 25 to 34 | 10.4% | 6.2% | 13.8% |
| Age 35 to 44 | 14.1% | 11.6% | 12.9% |
| Age 45 to 54 | 12.5% | 18.7% | 12.6% |
| Age 55 to 59 | 6.8% | 7.6% | 6.7% |
| Age 60 to 64 | 6.5% | 5.8% | 6.3% |
| Age 65 to 74 | 10.9% | 5.1% | 9.6% |
| Age 75 to 84 | 6.8% | 7.0% | 4.5% |
| Age 85 and over | 1.5% | 0.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Gardendale, AL | Carbon Hill, AL | United States |
| White | 79.7% | 80.6% | 59.4% |
| Black | 11.4% | 15.4% | 12.2% |
| Asian | 0.6% | 0.0% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 1.7% | 0.0% | 0.4% |
| Two or More Races | 5.5% | 4.0% | 3.2% |
| Hispanic | 1.1% | 0.0% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Gardendale, AL | Carbon Hill, AL | United States |
| Married Population | 56.2% | 31.9% | 49.8% |
| Currently Married | 55.4% | 26.2% | 48.0% |
| Married but Separated | 0.7% | 5.7% | 1.8% |
| Single Population | 43.8% | 68.1% | 50.2% |
| Never Married | 24.5% | 30.3% | 33.8% |
| Divorced | 11.4% | 25.1% | 10.8% |
| Widowed | 7.9% | 12.7% | 5.6% |
| space5 | | | |
| Household Size | 2.46 | 2.33 | 2.60 |
| Households | 6,393 | 652 | 124,010,992 |
| Family Households | 4,357 | 341 | 80,755,759 |
| Married couple, w/children | 26.7% | 32.0% | 30.5% |
| Married couple, no children | 53.1% | 16.7% | 42.9% |
| Non Family Households | 2,036 | 311 | 43,255,233 |
| Single householder, w/children | 9.0% | 23.8% | 15.8% |
| Single householder, no children | 11.2% | 27.6% | 10.8% |