| | Millbrae, CA | Alameda, CA | United States |
| Population | 23,083 | 78,320 | 329,725,481 |
| Female Population | 51.5% | 51.5% | 50.5% |
| Male Population | 48.6% | 48.6% | 49.5% |
| Median Age | 44.9 | 40.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 21,594 | 73,901 | 309,327,143 |
| Population - 2000 | 20,718 | 72,259 | 285,036,114 |
| Population - 1990 | 20,412 | 76,459 | 251,960,433 |
| Pop. 2000 to Now | 9.2% | 9.1% | 15.6% |
| Pop. 1990 to Now | 10.9% | 3.1% | 30.8% |
| space4 | | | |
| Population Density | 7,100.3 | 7,500.5 | 93.4 |
| Land Area | 3.3 | 10.4 | 3,531,905.4 |
| Water Area | 0.0 | 12.7 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Millbrae, CA | Alameda, CA | United States |
| Age 0 to 4 | 5.6% | 6.0% | 5.9% |
| Age 5 to 9 | 4.9% | 6.2% | 6.1% |
| Age 10 to 14 | 4.7% | 5.7% | 6.6% |
| Age 15 to 17 | 4.2% | 3.2% | 3.9% |
| Age 18 to 20 | 3.1% | 2.4% | 4.0% |
| Age 21 to 24 | 3.3% | 3.3% | 5.2% |
| Age 25 to 34 | 11.8% | 14.3% | 13.8% |
| Age 35 to 44 | 12.5% | 15.8% | 12.9% |
| Age 45 to 54 | 15.8% | 14.0% | 12.6% |
| Age 55 to 59 | 8.0% | 5.3% | 6.7% |
| Age 60 to 64 | 6.4% | 7.0% | 6.3% |
| Age 65 to 74 | 10.1% | 10.9% | 9.6% |
| Age 75 to 84 | 5.0% | 3.6% | 4.5% |
| Age 85 and over | 4.6% | 2.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | Millbrae, CA | Alameda, CA | United States |
| White | 33.9% | 42.1% | 59.4% |
| Black | 0.4% | 6.0% | 12.2% |
| Asian | 47.8% | 31.0% | 5.6% |
| Native American | 0.1% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 1.4% | 0.5% | 0.2% |
| Other | 1.8% | 1.1% | 0.4% |
| Two or More Races | 4.5% | 6.6% | 3.2% |
| Hispanic | 10.1% | 12.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Millbrae, CA | Alameda, CA | United States |
| Married Population | 53.5% | 52.9% | 49.8% |
| Currently Married | 52.3% | 51.6% | 48.0% |
| Married but Separated | 1.2% | 1.3% | 1.8% |
| Single Population | 46.5% | 47.1% | 50.2% |
| Never Married | 29.8% | 32.8% | 33.8% |
| Divorced | 10.1% | 9.1% | 10.8% |
| Widowed | 6.5% | 5.1% | 5.6% |
| space5 | | | |
| Household Size | 2.82 | 2.53 | 2.60 |
| Households | 8,108 | 30,500 | 124,010,992 |
| Family Households | 5,665 | 19,002 | 80,755,759 |
| Married couple, w/children | 35.6% | 37.9% | 30.5% |
| Married couple, no children | 42.3% | 40.9% | 42.9% |
| Non Family Households | 2,443 | 11,498 | 43,255,233 |
| Single householder, w/children | 9.8% | 11.7% | 15.8% |
| Single householder, no children | 12.3% | 9.6% | 10.8% |