| | Niles, OH | Girard, OH | United States |
| Population | 18,319 | 9,571 | 329,725,481 |
| Female Population | 53.1% | 53.3% | 50.5% |
| Male Population | 46.9% | 46.7% | 49.5% |
| Median Age | 45.4 | 38.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 19,153 | 9,908 | 309,327,143 |
| Population - 2000 | 20,932 | 10,902 | 285,036,114 |
| Population - 1990 | 21,128 | 11,304 | 251,960,433 |
| Pop. 2000 to Now | -13.8% | -16.0% | 15.6% |
| Pop. 1990 to Now | -14.6% | -19.0% | 30.8% |
| space4 | | | |
| Population Density | 2,127.9 | 1,671.8 | 93.4 |
| Land Area | 8.6 | 5.7 | 3,531,905.4 |
| Water Area | 0.0 | 0.5 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Niles, OH | Girard, OH | United States |
| Age 0 to 4 | 3.5% | 8.0% | 5.9% |
| Age 5 to 9 | 4.0% | 6.4% | 6.1% |
| Age 10 to 14 | 5.0% | 5.7% | 6.6% |
| Age 15 to 17 | 3.7% | 2.7% | 3.9% |
| Age 18 to 20 | 3.4% | 3.2% | 4.0% |
| Age 21 to 24 | 5.1% | 5.8% | 5.2% |
| Age 25 to 34 | 11.8% | 14.3% | 13.8% |
| Age 35 to 44 | 12.9% | 10.9% | 12.9% |
| Age 45 to 54 | 11.7% | 11.7% | 12.6% |
| Age 55 to 59 | 7.2% | 5.9% | 6.7% |
| Age 60 to 64 | 7.4% | 8.2% | 6.3% |
| Age 65 to 74 | 14.1% | 11.5% | 9.6% |
| Age 75 to 84 | 7.4% | 3.9% | 4.5% |
| Age 85 and over | 2.6% | 1.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Niles, OH | Girard, OH | United States |
| White | 90.0% | 89.0% | 59.4% |
| Black | 4.8% | 5.1% | 12.2% |
| Asian | 1.2% | 0.0% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.3% | 0.4% |
| Two or More Races | 2.5% | 2.7% | 3.2% |
| Hispanic | 1.5% | 2.9% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Niles, OH | Girard, OH | United States |
| Married Population | 41.9% | 43.9% | 49.8% |
| Currently Married | 40.4% | 42.1% | 48.0% |
| Married but Separated | 1.5% | 1.8% | 1.8% |
| Single Population | 58.1% | 56.1% | 50.2% |
| Never Married | 34.4% | 35.6% | 33.8% |
| Divorced | 15.0% | 13.4% | 10.8% |
| Widowed | 8.7% | 7.1% | 5.6% |
| space5 | | | |
| Household Size | 2.16 | 2.35 | 2.60 |
| Households | 8,367 | 4,063 | 124,010,992 |
| Family Households | 4,429 | 2,399 | 80,755,759 |
| Married couple, w/children | 21.0% | 26.3% | 30.5% |
| Married couple, no children | 47.3% | 37.7% | 42.9% |
| Non Family Households | 3,938 | 1,664 | 43,255,233 |
| Single householder, w/children | 19.1% | 26.2% | 15.8% |
| Single householder, no children | 12.6% | 9.9% | 10.8% |