| | Sellersville, PA | Bethlehem township, PA | United States |
| Population | 4,528 | 25,662 | 329,725,481 |
| Female Population | 47.3% | 50.5% | 50.5% |
| Male Population | 52.7% | 49.5% | 49.5% |
| Median Age | 38.2 | 43.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 4,250 | 23,794 | 309,327,143 |
| Population - 2000 | 4,564 | 21,171 | 285,036,114 |
| Population - 1990 | 4,479 | 16,425 | 251,960,433 |
| Pop. 2000 to Now | -6.4% | 16.0% | 15.6% |
| Pop. 1990 to Now | -4.6% | 49.5% | 30.8% |
| space4 | | | |
| Population Density | 3,958.0 | 1,778.1 | 93.4 |
| Land Area | 1.1 | 14.4 | 3,531,905.4 |
| Water Area | 0.0 | 0.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Sellersville, PA | Bethlehem township, PA | United States |
| Age 0 to 4 | 5.4% | 5.2% | 5.9% |
| Age 5 to 9 | 7.6% | 4.0% | 6.1% |
| Age 10 to 14 | 3.9% | 5.7% | 6.6% |
| Age 15 to 17 | 3.8% | 3.9% | 3.9% |
| Age 18 to 20 | 2.4% | 4.8% | 4.0% |
| Age 21 to 24 | 8.0% | 4.6% | 5.2% |
| Age 25 to 34 | 15.0% | 12.9% | 13.8% |
| Age 35 to 44 | 14.4% | 11.0% | 12.9% |
| Age 45 to 54 | 10.1% | 12.0% | 12.6% |
| Age 55 to 59 | 9.3% | 8.5% | 6.7% |
| Age 60 to 64 | 9.0% | 8.3% | 6.3% |
| Age 65 to 74 | 7.6% | 10.4% | 9.6% |
| Age 75 to 84 | 3.4% | 5.3% | 4.5% |
| Age 85 and over | 0.2% | 3.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Sellersville, PA | Bethlehem township, PA | United States |
| White | 81.6% | 74.0% | 59.4% |
| Black | 0.0% | 5.6% | 12.2% |
| Asian | 0.4% | 5.3% | 5.6% |
| Native American | 0.6% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.5% | 0.2% |
| Other | 0.9% | 0.4% | 0.4% |
| Two or More Races | 4.2% | 1.5% | 3.2% |
| Hispanic | 12.3% | 12.7% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Sellersville, PA | Bethlehem township, PA | United States |
| Married Population | 51.7% | 57.6% | 49.8% |
| Currently Married | 48.5% | 55.6% | 48.0% |
| Married but Separated | 3.2% | 2.0% | 1.8% |
| Single Population | 48.3% | 42.4% | 50.2% |
| Never Married | 32.7% | 28.6% | 33.8% |
| Divorced | 13.2% | 7.6% | 10.8% |
| Widowed | 2.4% | 6.2% | 5.6% |
| space5 | | | |
| Household Size | 2.51 | 2.55 | 2.60 |
| Households | 1,780 | 9,760 | 124,010,992 |
| Family Households | 1,213 | 6,924 | 80,755,759 |
| Married couple, w/children | 30.3% | 31.3% | 30.5% |
| Married couple, no children | 41.1% | 51.6% | 42.9% |
| Non Family Households | 567 | 2,836 | 43,255,233 |
| Single householder, w/children | 14.4% | 8.7% | 15.8% |
| Single householder, no children | 14.1% | 8.4% | 10.8% |