| | Kirby, TX | Heath, TX | United States |
| Population | 8,134 | 9,362 | 329,725,481 |
| Female Population | 49.5% | 47.3% | 50.5% |
| Male Population | 50.5% | 52.7% | 49.5% |
| Median Age | 37.9 | 44.8 | 38.4 |
| space3 | | | |
| Population - 2010 | 8,022 | 7,337 | 309,327,143 |
| Population - 2000 | 8,673 | 4,149 | 285,036,114 |
| Population - 1990 | 8,326 | 2,108 | 251,960,433 |
| Pop. 2000 to Now | 0.5% | 134.2% | 15.6% |
| Pop. 1990 to Now | 4.7% | 361.0% | 30.8% |
| space4 | | | |
| Population Density | 4,210.1 | 778.2 | 93.4 |
| Land Area | 1.9 | 12.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Kirby, TX | Heath, TX | United States |
| Age 0 to 4 | 9.7% | 4.2% | 5.9% |
| Age 5 to 9 | 5.4% | 7.8% | 6.1% |
| Age 10 to 14 | 8.2% | 8.4% | 6.6% |
| Age 15 to 17 | 3.3% | 6.5% | 3.9% |
| Age 18 to 20 | 4.0% | 3.4% | 4.0% |
| Age 21 to 24 | 5.4% | 3.7% | 5.2% |
| Age 25 to 34 | 10.3% | 3.0% | 13.8% |
| Age 35 to 44 | 13.0% | 13.6% | 12.9% |
| Age 45 to 54 | 9.9% | 14.6% | 12.6% |
| Age 55 to 59 | 5.9% | 8.4% | 6.7% |
| Age 60 to 64 | 5.0% | 10.0% | 6.3% |
| Age 65 to 74 | 12.9% | 10.7% | 9.6% |
| Age 75 to 84 | 6.4% | 4.6% | 4.5% |
| Age 85 and over | 0.6% | 1.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Kirby, TX | Heath, TX | United States |
| White | 22.9% | 85.0% | 59.4% |
| Black | 12.2% | 1.0% | 12.2% |
| Asian | 2.0% | 3.5% | 5.6% |
| Native American | 0.1% | 0.6% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 3.6% | 1.7% | 3.2% |
| Hispanic | 59.2% | 8.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Kirby, TX | Heath, TX | United States |
| Married Population | 52.3% | 70.5% | 49.8% |
| Currently Married | 47.9% | 70.3% | 48.0% |
| Married but Separated | 4.5% | 0.2% | 1.8% |
| Single Population | 47.7% | 29.5% | 50.2% |
| Never Married | 31.1% | 19.5% | 33.8% |
| Divorced | 11.6% | 5.1% | 10.8% |
| Widowed | 5.0% | 4.9% | 5.6% |
| space5 | | | |
| Household Size | 2.85 | 3.02 | 2.60 |
| Households | 2,850 | 3,101 | 124,010,992 |
| Family Households | 2,017 | 2,720 | 80,755,759 |
| Married couple, w/children | 29.5% | 42.5% | 30.5% |
| Married couple, no children | 34.4% | 51.2% | 42.9% |
| Non Family Households | 833 | 381 | 43,255,233 |
| Single householder, w/children | 21.4% | 3.8% | 15.8% |
| Single householder, no children | 14.8% | 2.4% | 10.8% |