| | Melville, NY | Commack, NY | United States |
| Population | 18,561 | 36,252 | 329,725,481 |
| Female Population | 54.2% | 50.4% | 50.5% |
| Male Population | 45.8% | 49.6% | 49.5% |
| Median Age | 51 | 45 | 38.4 |
| space3 | | | |
| Population - 2010 | 19,050 | 36,153 | 309,327,143 |
| Population - 2000 | 14,533 | 36,367 | 285,036,114 |
| Population - 1990 | 12,586 | 36,124 | 251,960,433 |
| Pop. 2000 to Now | 25.2% | 0.9% | 15.6% |
| Pop. 1990 to Now | 44.6% | 1.5% | 30.8% |
| space4 | | | |
| Population Density | 1,534.9 | 3,031.1 | 93.4 |
| Land Area | 12.1 | 12.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Melville, NY | Commack, NY | United States |
| Age 0 to 4 | 5.1% | 5.2% | 5.9% |
| Age 5 to 9 | 5.9% | 4.9% | 6.1% |
| Age 10 to 14 | 4.8% | 6.9% | 6.6% |
| Age 15 to 17 | 2.7% | 4.6% | 3.9% |
| Age 18 to 20 | 1.5% | 3.8% | 4.0% |
| Age 21 to 24 | 3.5% | 5.6% | 5.2% |
| Age 25 to 34 | 10.0% | 9.8% | 13.8% |
| Age 35 to 44 | 11.0% | 9.2% | 12.9% |
| Age 45 to 54 | 12.1% | 17.0% | 12.6% |
| Age 55 to 59 | 6.1% | 8.7% | 6.7% |
| Age 60 to 64 | 9.3% | 7.2% | 6.3% |
| Age 65 to 74 | 12.6% | 8.8% | 9.6% |
| Age 75 to 84 | 9.3% | 5.0% | 4.5% |
| Age 85 and over | 6.0% | 3.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | Melville, NY | Commack, NY | United States |
| White | 85.1% | 84.2% | 59.4% |
| Black | 2.0% | 1.1% | 12.2% |
| Asian | 6.7% | 5.0% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.1% | 0.1% | 0.4% |
| Two or More Races | 2.0% | 1.7% | 3.2% |
| Hispanic | 4.1% | 7.9% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Melville, NY | Commack, NY | United States |
| Married Population | 53.9% | 60.4% | 49.8% |
| Currently Married | 52.3% | 60.2% | 48.0% |
| Married but Separated | 1.7% | 0.2% | 1.8% |
| Single Population | 46.1% | 39.6% | 50.2% |
| Never Married | 22.8% | 27.9% | 33.8% |
| Divorced | 9.1% | 5.8% | 10.8% |
| Widowed | 14.2% | 5.9% | 5.6% |
| space5 | | | |
| Household Size | 2.55 | 3.09 | 2.60 |
| Households | 7,159 | 11,583 | 124,010,992 |
| Family Households | 4,675 | 9,672 | 80,755,759 |
| Married couple, w/children | 29.0% | 37.4% | 30.5% |
| Married couple, no children | 54.5% | 50.2% | 42.9% |
| Non Family Households | 2,484 | 1,911 | 43,255,233 |
| Single householder, w/children | 7.9% | 3.2% | 15.8% |
| Single householder, no children | 8.6% | 9.2% | 10.8% |