| | Calera, AL | Rockville, MD | United States |
| Population | 16,126 | 67,095 | 329,725,481 |
| Female Population | 52.3% | 51.9% | 50.5% |
| Male Population | 47.7% | 48.1% | 49.5% |
| Median Age | 32.4 | 39.2 | 38.4 |
| space3 | | | |
| Population - 2010 | 11,728 | 61,542 | 309,327,143 |
| Population - 2000 | 3,158 | 47,388 | 285,036,114 |
| Population - 1990 | 2,136 | 44,835 | 251,960,433 |
| Pop. 2000 to Now | 382.8% | 46.7% | 15.6% |
| Pop. 1990 to Now | 613.9% | 55.0% | 30.8% |
| space4 | | | |
| Population Density | 667.2 | 4,936.0 | 93.4 |
| Land Area | 24.2 | 13.6 | 3,531,905.4 |
| Water Area | 0.3 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Calera, AL | Rockville, MD | United States |
| Age 0 to 4 | 7.6% | 5.4% | 5.9% |
| Age 5 to 9 | 8.3% | 6.0% | 6.1% |
| Age 10 to 14 | 8.3% | 6.5% | 6.6% |
| Age 15 to 17 | 3.2% | 3.2% | 3.9% |
| Age 18 to 20 | 3.3% | 2.7% | 4.0% |
| Age 21 to 24 | 5.5% | 4.5% | 5.2% |
| Age 25 to 34 | 19.3% | 14.5% | 13.8% |
| Age 35 to 44 | 16.6% | 15.2% | 12.9% |
| Age 45 to 54 | 12.8% | 12.7% | 12.6% |
| Age 55 to 59 | 3.9% | 6.4% | 6.7% |
| Age 60 to 64 | 3.0% | 5.6% | 6.3% |
| Age 65 to 74 | 4.9% | 9.0% | 9.6% |
| Age 75 to 84 | 2.5% | 5.8% | 4.5% |
| Age 85 and over | 0.9% | 2.6% | 1.9% |
| space1 | | | |
| Race | | | |
| | Calera, AL | Rockville, MD | United States |
| White | 63.3% | 47.7% | 59.4% |
| Black | 28.4% | 10.1% | 12.2% |
| Asian | 0.5% | 20.3% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.1% | 1.1% | 0.4% |
| Two or More Races | 0.9% | 4.7% | 3.2% |
| Hispanic | 6.8% | 16.0% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Calera, AL | Rockville, MD | United States |
| Married Population | 56.1% | 53.6% | 49.8% |
| Currently Married | 54.6% | 52.2% | 48.0% |
| Married but Separated | 1.5% | 1.4% | 1.8% |
| Single Population | 43.9% | 46.4% | 50.2% |
| Never Married | 26.1% | 31.6% | 33.8% |
| Divorced | 13.6% | 9.4% | 10.8% |
| Widowed | 4.1% | 5.3% | 5.6% |
| space5 | | | |
| Household Size | 2.70 | 2.50 | 2.60 |
| Households | 5,971 | 26,536 | 124,010,992 |
| Family Households | 4,298 | 17,039 | 80,755,759 |
| Married couple, w/children | 41.4% | 33.7% | 30.5% |
| Married couple, no children | 31.1% | 41.4% | 42.9% |
| Non Family Households | 1,673 | 9,497 | 43,255,233 |
| Single householder, w/children | 18.9% | 12.7% | 15.8% |
| Single householder, no children | 8.6% | 12.2% | 10.8% |