| | Putnam, CT | Killingly, CT | United States |
| Population | 9,250 | 17,681 | 329,725,481 |
| Female Population | 52.6% | 52.9% | 50.5% |
| Male Population | 47.4% | 47.1% | 49.5% |
| Median Age | 44.3 | 42.2 | 38.4 |
| space3 | | | |
| Population - 2010 | 9,556 | 17,383 | 309,327,143 |
| Population - 2000 | 9,002 | 16,472 | 285,036,114 |
| Population - 1990 | 9,031 | 15,889 | 251,960,433 |
| Pop. 2000 to Now | 4.1% | 5.1% | 15.6% |
| Pop. 1990 to Now | 3.8% | 8.9% | 30.8% |
| space4 | | | |
| Population Density | 455.6 | 365.7 | 93.4 |
| Land Area | 20.3 | 48.4 | 3,531,905.4 |
| Water Area | 0.1 | 1.5 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Putnam, CT | Killingly, CT | United States |
| Age 0 to 4 | 5.1% | 4.8% | 5.9% |
| Age 5 to 9 | 5.2% | 6.8% | 6.1% |
| Age 10 to 14 | 6.3% | 5.8% | 6.6% |
| Age 15 to 17 | 3.9% | 3.1% | 3.9% |
| Age 18 to 20 | 4.1% | 2.7% | 4.0% |
| Age 21 to 24 | 2.7% | 3.8% | 5.2% |
| Age 25 to 34 | 12.7% | 11.9% | 13.8% |
| Age 35 to 44 | 10.7% | 13.8% | 12.9% |
| Age 45 to 54 | 17.7% | 14.3% | 12.6% |
| Age 55 to 59 | 8.0% | 7.6% | 6.7% |
| Age 60 to 64 | 6.4% | 7.3% | 6.3% |
| Age 65 to 74 | 8.4% | 10.9% | 9.6% |
| Age 75 to 84 | 4.5% | 4.9% | 4.5% |
| Age 85 and over | 4.2% | 2.2% | 1.9% |
| space1 | | | |
| Race | | | |
| | Putnam, CT | Killingly, CT | United States |
| White | 84.5% | 88.6% | 59.4% |
| Black | 0.7% | 1.2% | 12.2% |
| Asian | 1.1% | 0.8% | 5.6% |
| Native American | 0.1% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.1% | 0.4% | 0.4% |
| Two or More Races | 4.6% | 3.2% | 3.2% |
| Hispanic | 9.0% | 5.7% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Putnam, CT | Killingly, CT | United States |
| Married Population | 44.5% | 47.2% | 49.8% |
| Currently Married | 44.0% | 45.2% | 48.0% |
| Married but Separated | 0.6% | 2.1% | 1.8% |
| Single Population | 55.5% | 52.8% | 50.2% |
| Never Married | 32.5% | 30.7% | 33.8% |
| Divorced | 13.9% | 14.3% | 10.8% |
| Widowed | 9.0% | 7.8% | 5.6% |
| space5 | | | |
| Household Size | 2.39 | 2.44 | 2.60 |
| Households | 3,756 | 7,099 | 124,010,992 |
| Family Households | 2,285 | 4,463 | 80,755,759 |
| Married couple, w/children | 29.7% | 19.6% | 30.5% |
| Married couple, no children | 38.8% | 47.0% | 42.9% |
| Non Family Households | 1,471 | 2,636 | 43,255,233 |
| Single householder, w/children | 15.6% | 21.5% | 15.8% |
| Single householder, no children | 15.9% | 11.9% | 10.8% |