| | Castro Valley, CA | Redwood City, CA | United States |
| Population | 66,324 | 83,905 | 329,725,481 |
| Female Population | 51.4% | 49.6% | 50.5% |
| Male Population | 48.6% | 50.4% | 49.5% |
| Median Age | 42.4 | 37 | 38.4 |
| space3 | | | |
| Population - 2010 | 60,625 | 77,042 | 309,327,143 |
| Population - 2000 | 57,292 | 75,402 | 285,036,114 |
| Population - 1990 | 48,619 | 66,072 | 251,960,433 |
| Pop. 2000 to Now | 13.0% | 12.0% | 15.6% |
| Pop. 1990 to Now | 33.1% | 27.8% | 30.8% |
| space4 | | | |
| Population Density | 3,997.8 | 4,355.1 | 93.4 |
| Land Area | 16.6 | 19.3 | 3,531,905.4 |
| Water Area | 0.2 | 15.4 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Castro Valley, CA | Redwood City, CA | United States |
| Age 0 to 4 | 5.1% | 5.5% | 5.9% |
| Age 5 to 9 | 6.1% | 6.1% | 6.1% |
| Age 10 to 14 | 5.5% | 6.4% | 6.6% |
| Age 15 to 17 | 4.3% | 3.6% | 3.9% |
| Age 18 to 20 | 1.9% | 2.7% | 4.0% |
| Age 21 to 24 | 3.5% | 4.1% | 5.2% |
| Age 25 to 34 | 12.2% | 17.7% | 13.8% |
| Age 35 to 44 | 14.4% | 15.6% | 12.9% |
| Age 45 to 54 | 14.3% | 13.8% | 12.6% |
| Age 55 to 59 | 7.8% | 6.3% | 6.7% |
| Age 60 to 64 | 7.5% | 5.3% | 6.3% |
| Age 65 to 74 | 10.4% | 7.7% | 9.6% |
| Age 75 to 84 | 4.4% | 3.2% | 4.5% |
| Age 85 and over | 2.4% | 1.9% | 1.9% |
| space1 | | | |
| Race | | | |
| | Castro Valley, CA | Redwood City, CA | United States |
| White | 36.7% | 41.1% | 59.4% |
| Black | 9.3% | 1.9% | 12.2% |
| Asian | 31.2% | 16.2% | 5.6% |
| Native American | 0.5% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.2% | 0.8% | 0.2% |
| Other | 0.3% | 0.5% | 0.4% |
| Two or More Races | 4.8% | 3.9% | 3.2% |
| Hispanic | 16.9% | 35.3% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Castro Valley, CA | Redwood City, CA | United States |
| Married Population | 55.8% | 54.1% | 49.8% |
| Currently Married | 54.5% | 52.2% | 48.0% |
| Married but Separated | 1.3% | 2.0% | 1.8% |
| Single Population | 44.2% | 45.9% | 50.2% |
| Never Married | 29.8% | 34.2% | 33.8% |
| Divorced | 8.4% | 8.3% | 10.8% |
| Widowed | 6.0% | 3.4% | 5.6% |
| space5 | | | |
| Household Size | 2.90 | 2.74 | 2.60 |
| Households | 22,467 | 30,020 | 124,010,992 |
| Family Households | 16,692 | 20,164 | 80,755,759 |
| Married couple, w/children | 35.0% | 36.2% | 30.5% |
| Married couple, no children | 45.3% | 43.1% | 42.9% |
| Non Family Households | 5,775 | 9,856 | 43,255,233 |
| Single householder, w/children | 11.2% | 11.5% | 15.8% |
| Single householder, no children | 8.5% | 9.2% | 10.8% |