| | South Plainfield, NJ | Warren, NJ | United States |
| Population | 24,251 | 15,850 | 329,725,481 |
| Female Population | 50.0% | 48.0% | 50.5% |
| Male Population | 50.0% | 52.0% | 49.5% |
| Median Age | 41.2 | 45.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 23,387 | 15,350 | 309,327,143 |
| Population - 2000 | 21,810 | 14,259 | 285,036,114 |
| Population - 1990 | 20,489 | 10,830 | 251,960,433 |
| Pop. 2000 to Now | 9.9% | 9.7% | 15.6% |
| Pop. 1990 to Now | 17.0% | 44.4% | 30.8% |
| space4 | | | |
| Population Density | 2,923.2 | 810.7 | 93.4 |
| Land Area | 8.3 | 19.6 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | South Plainfield, NJ | Warren, NJ | United States |
| Age 0 to 4 | 6.3% | 4.9% | 5.9% |
| Age 5 to 9 | 4.8% | 3.9% | 6.1% |
| Age 10 to 14 | 5.2% | 9.0% | 6.6% |
| Age 15 to 17 | 3.9% | 5.9% | 3.9% |
| Age 18 to 20 | 2.7% | 3.2% | 4.0% |
| Age 21 to 24 | 4.1% | 3.4% | 5.2% |
| Age 25 to 34 | 15.2% | 7.5% | 13.8% |
| Age 35 to 44 | 13.6% | 11.5% | 12.9% |
| Age 45 to 54 | 12.9% | 16.0% | 12.6% |
| Age 55 to 59 | 7.6% | 9.9% | 6.7% |
| Age 60 to 64 | 6.4% | 7.3% | 6.3% |
| Age 65 to 74 | 10.6% | 10.3% | 9.6% |
| Age 75 to 84 | 4.6% | 5.2% | 4.5% |
| Age 85 and over | 2.0% | 1.9% | 1.9% |
| space1 | | | |
| Race | | | |
| | South Plainfield, NJ | Warren, NJ | United States |
| White | 52.5% | 70.9% | 59.4% |
| Black | 12.1% | 2.1% | 12.2% |
| Asian | 13.6% | 16.5% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.7% | 0.6% | 0.4% |
| Two or More Races | 3.0% | 2.2% | 3.2% |
| Hispanic | 18.1% | 7.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | South Plainfield, NJ | Warren, NJ | United States |
| Married Population | 59.1% | 65.7% | 49.8% |
| Currently Married | 58.6% | 65.3% | 48.0% |
| Married but Separated | 0.5% | 0.4% | 1.8% |
| Single Population | 40.9% | 34.3% | 50.2% |
| Never Married | 29.6% | 25.5% | 33.8% |
| Divorced | 5.9% | 5.2% | 10.8% |
| Widowed | 5.4% | 3.6% | 5.6% |
| space5 | | | |
| Household Size | 2.94 | 2.91 | 2.60 |
| Households | 8,144 | 5,386 | 124,010,992 |
| Family Households | 6,621 | 4,666 | 80,755,759 |
| Married couple, w/children | 38.0% | 40.8% | 30.5% |
| Married couple, no children | 45.0% | 47.2% | 42.9% |
| Non Family Households | 1,523 | 720 | 43,255,233 |
| Single householder, w/children | 7.6% | 4.0% | 15.8% |
| Single householder, no children | 9.4% | 8.0% | 10.8% |