| | Northfield, OH | Brook Park, OH | United States |
| Population | 3,550 | 18,592 | 329,725,481 |
| Female Population | 51.9% | 51.7% | 50.5% |
| Male Population | 48.1% | 48.4% | 49.5% |
| Median Age | 38 | 42 | 38.4 |
| space3 | | | |
| Population - 2010 | 3,671 | 19,174 | 309,327,143 |
| Population - 2000 | 3,827 | 21,218 | 285,036,114 |
| Population - 1990 | 3,624 | 22,865 | 251,960,433 |
| Pop. 2000 to Now | -4.7% | -14.0% | 15.6% |
| Pop. 1990 to Now | 0.7% | -20.2% | 30.8% |
| space4 | | | |
| Population Density | 3,377.7 | 2,470.7 | 93.4 |
| Land Area | 1.1 | 7.5 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Northfield, OH | Brook Park, OH | United States |
| Age 0 to 4 | 6.0% | 7.3% | 5.9% |
| Age 5 to 9 | 10.6% | 4.9% | 6.1% |
| Age 10 to 14 | 3.5% | 4.9% | 6.6% |
| Age 15 to 17 | 3.6% | 2.9% | 3.9% |
| Age 18 to 20 | 1.7% | 3.0% | 4.0% |
| Age 21 to 24 | 1.9% | 4.1% | 5.2% |
| Age 25 to 34 | 14.6% | 14.5% | 13.8% |
| Age 35 to 44 | 15.8% | 10.9% | 12.9% |
| Age 45 to 54 | 13.5% | 11.4% | 12.6% |
| Age 55 to 59 | 8.9% | 8.2% | 6.7% |
| Age 60 to 64 | 4.7% | 7.5% | 6.3% |
| Age 65 to 74 | 9.4% | 10.5% | 9.6% |
| Age 75 to 84 | 4.7% | 7.5% | 4.5% |
| Age 85 and over | 1.0% | 2.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Northfield, OH | Brook Park, OH | United States |
| White | 74.7% | 81.8% | 59.4% |
| Black | 11.7% | 4.3% | 12.2% |
| Asian | 8.9% | 3.5% | 5.6% |
| Native American | 0.9% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 2.3% | 4.4% | 3.2% |
| Hispanic | 1.4% | 5.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Northfield, OH | Brook Park, OH | United States |
| Married Population | 50.9% | 46.7% | 49.8% |
| Currently Married | 50.7% | 45.1% | 48.0% |
| Married but Separated | 0.2% | 1.6% | 1.8% |
| Single Population | 49.1% | 53.3% | 50.2% |
| Never Married | 30.1% | 31.9% | 33.8% |
| Divorced | 12.5% | 13.1% | 10.8% |
| Widowed | 6.6% | 8.3% | 5.6% |
| space5 | | | |
| Household Size | 2.54 | 2.41 | 2.60 |
| Households | 1,400 | 7,671 | 124,010,992 |
| Family Households | 948 | 4,805 | 80,755,759 |
| Married couple, w/children | 33.2% | 25.3% | 30.5% |
| Married couple, no children | 35.4% | 43.0% | 42.9% |
| Non Family Households | 452 | 2,866 | 43,255,233 |
| Single householder, w/children | 14.7% | 14.9% | 15.8% |
| Single householder, no children | 16.7% | 16.7% | 10.8% |