| | Islip Terrace, NY | Islip, NY | United States |
| Population | 5,542 | 339,596 | 329,725,481 |
| Female Population | 49.5% | 50.0% | 50.5% |
| Male Population | 50.5% | 50.0% | 49.5% |
| Median Age | 40.7 | 38.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 5,742 | 335,540 | 309,327,143 |
| Population - 2000 | 5,641 | 322,612 | 285,036,114 |
| Population - 1990 | 5,530 | 299,587 | 251,960,433 |
| Pop. 2000 to Now | -1.7% | 1.9% | 15.6% |
| Pop. 1990 to Now | 0.3% | 9.8% | 30.8% |
| space4 | | | |
| Population Density | 4,129.7 | 3,268.4 | 93.4 |
| Land Area | 1.3 | 103.9 | 3,531,905.4 |
| Water Area | 0.0 | 59.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Islip Terrace, NY | Islip, NY | United States |
| Age 0 to 4 | 5.1% | 6.0% | 5.9% |
| Age 5 to 9 | 4.8% | 5.9% | 6.1% |
| Age 10 to 14 | 6.6% | 6.5% | 6.6% |
| Age 15 to 17 | 4.6% | 4.0% | 3.9% |
| Age 18 to 20 | 3.8% | 3.5% | 4.0% |
| Age 21 to 24 | 6.6% | 5.4% | 5.2% |
| Age 25 to 34 | 9.1% | 13.7% | 13.8% |
| Age 35 to 44 | 14.2% | 13.3% | 12.9% |
| Age 45 to 54 | 17.9% | 14.3% | 12.6% |
| Age 55 to 59 | 8.3% | 7.2% | 6.7% |
| Age 60 to 64 | 6.5% | 6.6% | 6.3% |
| Age 65 to 74 | 7.5% | 8.0% | 9.6% |
| Age 75 to 84 | 3.4% | 3.9% | 4.5% |
| Age 85 and over | 1.4% | 1.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Islip Terrace, NY | Islip, NY | United States |
| White | 79.2% | 51.5% | 59.4% |
| Black | 0.0% | 8.0% | 12.2% |
| Asian | 3.5% | 3.6% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.6% | 0.4% |
| Two or More Races | 1.6% | 1.5% | 3.2% |
| Hispanic | 15.6% | 34.7% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Islip Terrace, NY | Islip, NY | United States |
| Married Population | 59.1% | 49.6% | 49.8% |
| Currently Married | 57.2% | 47.6% | 48.0% |
| Married but Separated | 1.9% | 2.0% | 1.8% |
| Single Population | 40.9% | 50.4% | 50.2% |
| Never Married | 30.1% | 36.4% | 33.8% |
| Divorced | 5.8% | 8.8% | 10.8% |
| Widowed | 5.0% | 5.2% | 5.6% |
| space5 | | | |
| Household Size | 3.18 | 3.31 | 2.60 |
| Households | 1,742 | 101,741 | 124,010,992 |
| Family Households | 1,359 | 76,347 | 80,755,759 |
| Married couple, w/children | 37.1% | 33.5% | 30.5% |
| Married couple, no children | 45.4% | 40.4% | 42.9% |
| Non Family Households | 383 | 25,394 | 43,255,233 |
| Single householder, w/children | 7.4% | 12.8% | 15.8% |
| Single householder, no children | 10.2% | 13.4% | 10.8% |