| | Northfield, NJ | Avenel, NJ | United States |
| Population | 8,419 | 17,132 | 329,725,481 |
| Female Population | 52.0% | 41.1% | 50.5% |
| Male Population | 48.0% | 58.9% | 49.5% |
| Median Age | 44.7 | 39.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 8,517 | 17,087 | 309,327,143 |
| Population - 2000 | 7,725 | 17,552 | 285,036,114 |
| Population - 1990 | 7,305 | 15,504 | 251,960,433 |
| Pop. 2000 to Now | 4.2% | 7.0% | 15.6% |
| Pop. 1990 to Now | 10.2% | 21.2% | 30.8% |
| space4 | | | |
| Population Density | 2,350.4 | 4,923.0 | 93.4 |
| Land Area | 3.6 | 3.5 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Northfield, NJ | Avenel, NJ | United States |
| Age 0 to 4 | 2.5% | 4.8% | 5.9% |
| Age 5 to 9 | 5.7% | 6.1% | 6.1% |
| Age 10 to 14 | 7.8% | 6.4% | 6.6% |
| Age 15 to 17 | 4.2% | 3.8% | 3.9% |
| Age 18 to 20 | 4.8% | 2.2% | 4.0% |
| Age 21 to 24 | 3.0% | 3.2% | 5.2% |
| Age 25 to 34 | 10.3% | 15.7% | 13.8% |
| Age 35 to 44 | 12.3% | 13.4% | 12.9% |
| Age 45 to 54 | 13.6% | 17.4% | 12.6% |
| Age 55 to 59 | 8.8% | 7.9% | 6.7% |
| Age 60 to 64 | 8.8% | 6.3% | 6.3% |
| Age 65 to 74 | 8.6% | 8.5% | 9.6% |
| Age 75 to 84 | 7.3% | 2.8% | 4.5% |
| Age 85 and over | 2.3% | 1.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Northfield, NJ | Avenel, NJ | United States |
| White | 75.8% | 32.2% | 59.4% |
| Black | 2.4% | 22.4% | 12.2% |
| Asian | 7.7% | 20.5% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.3% | 0.7% | 0.4% |
| Two or More Races | 0.9% | 1.1% | 3.2% |
| Hispanic | 12.9% | 23.0% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Northfield, NJ | Avenel, NJ | United States |
| Married Population | 50.7% | 44.6% | 49.8% |
| Currently Married | 49.9% | 42.9% | 48.0% |
| Married but Separated | 0.8% | 1.7% | 1.8% |
| Single Population | 49.3% | 55.4% | 50.2% |
| Never Married | 30.1% | 39.3% | 33.8% |
| Divorced | 12.1% | 10.9% | 10.8% |
| Widowed | 7.2% | 5.2% | 5.6% |
| space5 | | | |
| Household Size | 2.68 | 2.65 | 2.60 |
| Households | 3,084 | 5,055 | 124,010,992 |
| Family Households | 2,120 | 3,406 | 80,755,759 |
| Married couple, w/children | 35.1% | 42.4% | 30.5% |
| Married couple, no children | 42.2% | 30.1% | 42.9% |
| Non Family Households | 964 | 1,649 | 43,255,233 |
| Single householder, w/children | 8.6% | 17.8% | 15.8% |
| Single householder, no children | 14.1% | 9.8% | 10.8% |