| | Millis, MA | Dover, MA | United States |
| Population | 8,481 | 5,894 | 329,725,481 |
| Female Population | 51.2% | 48.2% | 50.5% |
| Male Population | 48.8% | 51.8% | 49.5% |
| Median Age | 45.8 | 45.2 | 38.4 |
| space3 | | | |
| Population - 2010 | 7,913 | 5,603 | 309,327,143 |
| Population - 2000 | 7,902 | 5,558 | 285,036,114 |
| Population - 1990 | 7,613 | 4,915 | 251,960,433 |
| Pop. 2000 to Now | 7.8% | 10.1% | 15.6% |
| Pop. 1990 to Now | 11.9% | 24.5% | 30.8% |
| space4 | | | |
| Population Density | 705.5 | 389.8 | 93.4 |
| Land Area | 12.0 | 15.1 | 3,531,905.4 |
| Water Area | 0.2 | 0.3 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Millis, MA | Dover, MA | United States |
| Age 0 to 4 | 5.6% | 4.6% | 5.9% |
| Age 5 to 9 | 4.8% | 7.0% | 6.1% |
| Age 10 to 14 | 6.0% | 8.6% | 6.6% |
| Age 15 to 17 | 4.7% | 8.1% | 3.9% |
| Age 18 to 20 | 3.4% | 2.9% | 4.0% |
| Age 21 to 24 | 4.0% | 5.5% | 5.2% |
| Age 25 to 34 | 8.5% | 3.6% | 13.8% |
| Age 35 to 44 | 10.9% | 9.4% | 12.9% |
| Age 45 to 54 | 13.5% | 16.1% | 12.6% |
| Age 55 to 59 | 8.4% | 11.7% | 6.7% |
| Age 60 to 64 | 8.9% | 6.1% | 6.3% |
| Age 65 to 74 | 15.8% | 10.2% | 9.6% |
| Age 75 to 84 | 4.0% | 4.0% | 4.5% |
| Age 85 and over | 1.4% | 2.2% | 1.9% |
| space1 | | | |
| Race | | | |
| | Millis, MA | Dover, MA | United States |
| White | 89.4% | 77.1% | 59.4% |
| Black | 1.7% | 0.0% | 12.2% |
| Asian | 3.1% | 12.7% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 1.0% | 0.9% | 0.4% |
| Two or More Races | 3.1% | 4.8% | 3.2% |
| Hispanic | 1.7% | 4.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Millis, MA | Dover, MA | United States |
| Married Population | 61.3% | 69.3% | 49.8% |
| Currently Married | 59.7% | 68.2% | 48.0% |
| Married but Separated | 1.6% | 1.1% | 1.8% |
| Single Population | 38.7% | 30.7% | 50.2% |
| Never Married | 27.7% | 23.5% | 33.8% |
| Divorced | 7.4% | 4.0% | 10.8% |
| Widowed | 3.6% | 3.2% | 5.6% |
| space5 | | | |
| Household Size | 2.74 | 3.08 | 2.60 |
| Households | 3,078 | 1,916 | 124,010,992 |
| Family Households | 2,437 | 1,670 | 80,755,759 |
| Married couple, w/children | 29.5% | 48.6% | 30.5% |
| Married couple, no children | 53.2% | 42.4% | 42.9% |
| Non Family Households | 641 | 246 | 43,255,233 |
| Single householder, w/children | 7.1% | 6.5% | 15.8% |
| Single householder, no children | 10.3% | 2.6% | 10.8% |