| | Cambridge, MA | Watertown Town, MA | United States |
| Population | 116,892 | 35,171 | 329,725,481 |
| Female Population | 50.0% | 53.6% | 50.5% |
| Male Population | 50.0% | 46.4% | 49.5% |
| Median Age | 30.5 | 39 | 38.4 |
| space3 | | | |
| Population - 2010 | 105,017 | 32,058 | 309,327,143 |
| Population - 2000 | 101,355 | 32,986 | 285,036,114 |
| Population - 1990 | 95,802 | 33,284 | 251,960,433 |
| Pop. 2000 to Now | 17.6% | 9.5% | 15.6% |
| Pop. 1990 to Now | 24.4% | 8.5% | 30.8% |
| space4 | | | |
| Population Density | 18,284.4 | 8,795.0 | 93.4 |
| Land Area | 6.4 | 4.0 | 3,531,905.4 |
| Water Area | 0.7 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Cambridge, MA | Watertown Town, MA | United States |
| Age 0 to 4 | 4.3% | 5.8% | 5.9% |
| Age 5 to 9 | 3.5% | 2.9% | 6.1% |
| Age 10 to 14 | 2.8% | 3.5% | 6.6% |
| Age 15 to 17 | 1.9% | 2.2% | 3.9% |
| Age 18 to 20 | 9.2% | 2.6% | 4.0% |
| Age 21 to 24 | 10.9% | 3.6% | 5.2% |
| Age 25 to 34 | 27.8% | 21.4% | 13.8% |
| Age 35 to 44 | 13.3% | 15.5% | 12.9% |
| Age 45 to 54 | 7.7% | 11.2% | 12.6% |
| Age 55 to 59 | 3.6% | 6.5% | 6.7% |
| Age 60 to 64 | 3.8% | 7.4% | 6.3% |
| Age 65 to 74 | 6.8% | 9.9% | 9.6% |
| Age 75 to 84 | 3.0% | 5.0% | 4.5% |
| Age 85 and over | 1.5% | 2.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Cambridge, MA | Watertown Town, MA | United States |
| White | 57.5% | 72.5% | 59.4% |
| Black | 10.0% | 3.6% | 12.2% |
| Asian | 18.2% | 11.9% | 5.6% |
| Native American | 0.1% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.0% | 0.2% |
| Other | 0.8% | 0.2% | 0.4% |
| Two or More Races | 4.6% | 4.1% | 3.2% |
| Hispanic | 8.8% | 7.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Cambridge, MA | Watertown Town, MA | United States |
| Married Population | 33.9% | 50.0% | 49.8% |
| Currently Married | 33.1% | 48.8% | 48.0% |
| Married but Separated | 0.7% | 1.1% | 1.8% |
| Single Population | 66.1% | 50.0% | 50.2% |
| Never Married | 57.9% | 37.7% | 33.8% |
| Divorced | 5.6% | 7.7% | 10.8% |
| Widowed | 2.6% | 4.7% | 5.6% |
| space5 | | | |
| Household Size | 2.09 | 2.18 | 2.60 |
| Households | 47,777 | 16,027 | 124,010,992 |
| Family Households | 19,584 | 8,748 | 80,755,759 |
| Married couple, w/children | 31.7% | 31.8% | 30.5% |
| Married couple, no children | 47.0% | 45.0% | 42.9% |
| Non Family Households | 28,193 | 7,279 | 43,255,233 |
| Single householder, w/children | 10.6% | 8.4% | 15.8% |
| Single householder, no children | 10.7% | 14.9% | 10.8% |