| | Holtsville, NY | Bay Shore, NY | United States |
| Population | 19,497 | 31,488 | 329,725,481 |
| Female Population | 50.6% | 48.8% | 50.5% |
| Male Population | 49.5% | 51.2% | 49.5% |
| Median Age | 39.3 | 35.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 19,277 | 27,916 | 309,327,143 |
| Population - 2000 | 17,006 | 23,852 | 285,036,114 |
| Population - 1990 | 14,972 | 21,279 | 251,960,433 |
| Pop. 2000 to Now | 17.4% | 25.9% | 15.6% |
| Pop. 1990 to Now | 33.3% | 41.1% | 30.8% |
| space4 | | | |
| Population Density | 2,742.6 | 5,830.0 | 93.4 |
| Land Area | 7.1 | 5.4 | 3,531,905.4 |
| Water Area | 0.0 | 0.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Holtsville, NY | Bay Shore, NY | United States |
| Age 0 to 4 | 5.7% | 7.5% | 5.9% |
| Age 5 to 9 | 6.2% | 8.8% | 6.1% |
| Age 10 to 14 | 6.4% | 8.2% | 6.6% |
| Age 15 to 17 | 3.9% | 4.1% | 3.9% |
| Age 18 to 20 | 3.8% | 2.4% | 4.0% |
| Age 21 to 24 | 5.5% | 4.1% | 5.2% |
| Age 25 to 34 | 11.8% | 13.6% | 13.8% |
| Age 35 to 44 | 13.6% | 15.5% | 12.9% |
| Age 45 to 54 | 16.5% | 13.4% | 12.6% |
| Age 55 to 59 | 7.5% | 6.1% | 6.7% |
| Age 60 to 64 | 6.2% | 6.2% | 6.3% |
| Age 65 to 74 | 8.2% | 5.4% | 9.6% |
| Age 75 to 84 | 3.5% | 3.1% | 4.5% |
| Age 85 and over | 1.2% | 1.6% | 1.9% |
| space1 | | | |
| Race | | | |
| | Holtsville, NY | Bay Shore, NY | United States |
| White | 77.9% | 37.1% | 59.4% |
| Black | 5.5% | 13.6% | 12.2% |
| Asian | 3.7% | 8.7% | 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 | 0.8% | 3.6% | 3.2% |
| Hispanic | 12.0% | 36.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Holtsville, NY | Bay Shore, NY | United States |
| Married Population | 54.4% | 45.3% | 49.8% |
| Currently Married | 52.8% | 43.5% | 48.0% |
| Married but Separated | 1.6% | 1.9% | 1.8% |
| Single Population | 45.6% | 54.7% | 50.2% |
| Never Married | 30.8% | 37.2% | 33.8% |
| Divorced | 10.0% | 10.8% | 10.8% |
| Widowed | 4.8% | 6.7% | 5.6% |
| space5 | | | |
| Household Size | 3.00 | 3.28 | 2.60 |
| Households | 6,474 | 9,517 | 124,010,992 |
| Family Households | 5,001 | 6,434 | 80,755,759 |
| Married couple, w/children | 34.5% | 35.3% | 30.5% |
| Married couple, no children | 40.9% | 33.1% | 42.9% |
| Non Family Households | 1,473 | 3,083 | 43,255,233 |
| Single householder, w/children | 11.9% | 18.2% | 15.8% |
| Single householder, no children | 12.7% | 13.5% | 10.8% |