| | Shirley, NY | Sayville, NY | United States |
| Population | 28,059 | 16,290 | 329,725,481 |
| Female Population | 48.2% | 51.3% | 50.5% |
| Male Population | 51.8% | 48.7% | 49.5% |
| Median Age | 39 | 44.2 | 38.4 |
| space3 | | | |
| Population - 2010 | 28,070 | 16,107 | 309,327,143 |
| Population - 2000 | 25,395 | 16,735 | 285,036,114 |
| Population - 1990 | 22,936 | 16,550 | 251,960,433 |
| Pop. 2000 to Now | 5.8% | -4.7% | 15.6% |
| Pop. 1990 to Now | 17.1% | -3.6% | 30.8% |
| space4 | | | |
| Population Density | 2,445.9 | 3,070.1 | 93.4 |
| Land Area | 11.5 | 5.3 | 3,531,905.4 |
| Water Area | 0.4 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Shirley, NY | Sayville, NY | United States |
| Age 0 to 4 | 5.6% | 4.7% | 5.9% |
| Age 5 to 9 | 7.0% | 7.5% | 6.1% |
| Age 10 to 14 | 6.5% | 6.8% | 6.6% |
| Age 15 to 17 | 3.3% | 3.5% | 3.9% |
| Age 18 to 20 | 4.4% | 2.8% | 4.0% |
| Age 21 to 24 | 5.5% | 5.1% | 5.2% |
| Age 25 to 34 | 12.1% | 9.4% | 13.8% |
| Age 35 to 44 | 14.0% | 11.1% | 12.9% |
| Age 45 to 54 | 11.6% | 15.6% | 12.6% |
| Age 55 to 59 | 10.9% | 6.7% | 6.7% |
| Age 60 to 64 | 5.9% | 6.8% | 6.3% |
| Age 65 to 74 | 9.7% | 10.3% | 9.6% |
| Age 75 to 84 | 1.9% | 5.0% | 4.5% |
| Age 85 and over | 1.5% | 4.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Shirley, NY | Sayville, NY | United States |
| White | 65.6% | 91.0% | 59.4% |
| Black | 7.3% | 1.0% | 12.2% |
| Asian | 3.4% | 1.5% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.1% | 0.2% | 0.4% |
| Two or More Races | 2.4% | 1.5% | 3.2% |
| Hispanic | 21.2% | 4.7% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Shirley, NY | Sayville, NY | United States |
| Married Population | 47.6% | 56.7% | 49.8% |
| Currently Married | 46.0% | 54.4% | 48.0% |
| Married but Separated | 1.6% | 2.3% | 1.8% |
| Single Population | 52.4% | 43.3% | 50.2% |
| Never Married | 36.7% | 28.4% | 33.8% |
| Divorced | 9.8% | 7.7% | 10.8% |
| Widowed | 5.9% | 7.1% | 5.6% |
| space5 | | | |
| Household Size | 3.40 | 2.78 | 2.60 |
| Households | 8,168 | 5,706 | 124,010,992 |
| Family Households | 6,403 | 4,277 | 80,755,759 |
| Married couple, w/children | 32.7% | 35.1% | 30.5% |
| Married couple, no children | 39.2% | 44.4% | 42.9% |
| Non Family Households | 1,765 | 1,429 | 43,255,233 |
| Single householder, w/children | 14.6% | 7.3% | 15.8% |
| Single householder, no children | 13.5% | 13.3% | 10.8% |