| | Westhampton, NY | Mattituck, NY | United States |
| Population | 3,816 | 4,584 | 329,725,481 |
| Female Population | 50.0% | 52.9% | 50.5% |
| Male Population | 50.0% | 47.1% | 49.5% |
| Median Age | 44.9 | 58.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 3,440 | 4,146 | 309,327,143 |
| Population - 2000 | 2,869 | 4,198 | 285,036,114 |
| Population - 1990 | 2,129 | 3,902 | 251,960,433 |
| Pop. 2000 to Now | -8.0% | 13.4% | 15.6% |
| Pop. 1990 to Now | 24.0% | 22.0% | 30.8% |
| space4 | | | |
| Population Density | 301.4 | 509.5 | 93.4 |
| Land Area | 12.7 | 9.0 | 3,531,905.4 |
| Water Area | 2.2 | 0.4 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Westhampton, NY | Mattituck, NY | United States |
| Age 0 to 4 | 8.0% | 2.1% | 5.9% |
| Age 5 to 9 | 9.0% | 1.4% | 6.1% |
| Age 10 to 14 | 4.6% | 4.1% | 6.6% |
| Age 15 to 17 | 7.9% | 5.7% | 3.9% |
| Age 18 to 20 | 2.6% | 3.9% | 4.0% |
| Age 21 to 24 | 1.9% | 2.4% | 5.2% |
| Age 25 to 34 | 7.0% | 7.6% | 13.8% |
| Age 35 to 44 | 8.9% | 10.4% | 12.9% |
| Age 45 to 54 | 11.5% | 9.8% | 12.6% |
| Age 55 to 59 | 7.7% | 9.6% | 6.7% |
| Age 60 to 64 | 6.0% | 10.6% | 6.3% |
| Age 65 to 74 | 13.4% | 19.5% | 9.6% |
| Age 75 to 84 | 7.5% | 9.8% | 4.5% |
| Age 85 and over | 4.0% | 3.2% | 1.9% |
| space1 | | | |
| Race | | | |
| | Westhampton, NY | Mattituck, NY | United States |
| White | 80.5% | 93.9% | 59.4% |
| Black | 0.8% | 0.0% | 12.2% |
| Asian | 2.6% | 0.0% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 2.9% | 0.0% | 0.4% |
| Two or More Races | 4.9% | 0.4% | 3.2% |
| Hispanic | 8.2% | 5.7% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Westhampton, NY | Mattituck, NY | United States |
| Married Population | 60.2% | 57.8% | 49.8% |
| Currently Married | 59.6% | 57.3% | 48.0% |
| Married but Separated | 0.5% | 0.4% | 1.8% |
| Single Population | 39.8% | 42.2% | 50.2% |
| Never Married | 27.6% | 22.5% | 33.8% |
| Divorced | 6.2% | 12.0% | 10.8% |
| Widowed | 6.1% | 7.6% | 5.6% |
| space5 | | | |
| Household Size | 3.06 | 2.25 | 2.60 |
| Households | 1,193 | 2,028 | 124,010,992 |
| Family Households | 953 | 1,485 | 80,755,759 |
| Married couple, w/children | 37.0% | 18.6% | 30.5% |
| Married couple, no children | 52.3% | 63.1% | 42.9% |
| Non Family Households | 240 | 543 | 43,255,233 |
| Single householder, w/children | 6.2% | 5.9% | 15.8% |
| Single householder, no children | 4.5% | 12.4% | 10.8% |