| | Hayward, CA | Castro Valley, CA | United States |
| Population | 162,254 | 66,324 | 329,725,481 |
| Female Population | 49.3% | 51.4% | 50.5% |
| Male Population | 50.7% | 48.6% | 49.5% |
| Median Age | 36.6 | 42.4 | 38.4 |
| space3 | | | |
| Population - 2010 | 144,662 | 60,625 | 309,327,143 |
| Population - 2000 | 140,030 | 57,292 | 285,036,114 |
| Population - 1990 | 111,498 | 48,619 | 251,960,433 |
| Pop. 2000 to Now | 12.8% | 13.0% | 15.6% |
| Pop. 1990 to Now | 41.7% | 33.1% | 30.8% |
| space4 | | | |
| Population Density | 3,563.1 | 3,997.8 | 93.4 |
| Land Area | 45.5 | 16.6 | 3,531,905.4 |
| Water Area | 18.3 | 0.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Hayward, CA | Castro Valley, CA | United States |
| Age 0 to 4 | 5.9% | 5.1% | 5.9% |
| Age 5 to 9 | 5.4% | 6.1% | 6.1% |
| Age 10 to 14 | 5.9% | 5.5% | 6.6% |
| Age 15 to 17 | 3.9% | 4.3% | 3.9% |
| Age 18 to 20 | 3.7% | 1.9% | 4.0% |
| Age 21 to 24 | 5.2% | 3.5% | 5.2% |
| Age 25 to 34 | 17.3% | 12.2% | 13.8% |
| Age 35 to 44 | 14.4% | 14.4% | 12.9% |
| Age 45 to 54 | 13.0% | 14.3% | 12.6% |
| Age 55 to 59 | 6.7% | 7.8% | 6.7% |
| Age 60 to 64 | 5.9% | 7.5% | 6.3% |
| Age 65 to 74 | 7.6% | 10.4% | 9.6% |
| Age 75 to 84 | 3.5% | 4.4% | 4.5% |
| Age 85 and over | 1.6% | 2.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Hayward, CA | Castro Valley, CA | United States |
| White | 15.9% | 36.7% | 59.4% |
| Black | 9.1% | 9.3% | 12.2% |
| Asian | 28.7% | 31.2% | 5.6% |
| Native American | 0.3% | 0.5% | 0.6% |
| Hawaiian, Pacific Islander | 1.9% | 0.2% | 0.2% |
| Other | 0.4% | 0.3% | 0.4% |
| Two or More Races | 4.8% | 4.8% | 3.2% |
| Hispanic | 38.9% | 16.9% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Hayward, CA | Castro Valley, CA | United States |
| Married Population | 48.4% | 55.8% | 49.8% |
| Currently Married | 46.7% | 54.5% | 48.0% |
| Married but Separated | 1.8% | 1.3% | 1.8% |
| Single Population | 51.6% | 44.2% | 50.2% |
| Never Married | 38.5% | 29.8% | 33.8% |
| Divorced | 8.1% | 8.4% | 10.8% |
| Widowed | 5.0% | 6.0% | 5.6% |
| space5 | | | |
| Household Size | 3.21 | 2.90 | 2.60 |
| Households | 49,524 | 22,467 | 124,010,992 |
| Family Households | 36,296 | 16,692 | 80,755,759 |
| Married couple, w/children | 34.5% | 35.0% | 30.5% |
| Married couple, no children | 34.7% | 45.3% | 42.9% |
| Non Family Households | 13,228 | 5,775 | 43,255,233 |
| Single householder, w/children | 15.7% | 11.2% | 15.8% |
| Single householder, no children | 15.2% | 8.5% | 10.8% |