| | San Leandro, CA | Seaside, CA | United States |
| Population | 91,176 | 32,631 | 329,725,481 |
| Female Population | 50.8% | 49.9% | 50.5% |
| Male Population | 49.2% | 50.1% | 49.5% |
| Median Age | 40.9 | 33.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 85,108 | 33,178 | 309,327,143 |
| Population - 2000 | 79,452 | 31,696 | 285,036,114 |
| Population - 1990 | 68,223 | 38,901 | 251,960,433 |
| Pop. 2000 to Now | 12.2% | 7.6% | 15.6% |
| Pop. 1990 to Now | 30.7% | -12.3% | 30.8% |
| space4 | | | |
| Population Density | 6,834.3 | 3,531.5 | 93.4 |
| Land Area | 13.3 | 9.2 | 3,531,905.4 |
| Water Area | 2.2 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | San Leandro, CA | Seaside, CA | United States |
| Age 0 to 4 | 4.1% | 6.7% | 5.9% |
| Age 5 to 9 | 5.1% | 6.4% | 6.1% |
| Age 10 to 14 | 5.0% | 6.7% | 6.6% |
| Age 15 to 17 | 3.5% | 3.9% | 3.9% |
| Age 18 to 20 | 3.3% | 6.6% | 4.0% |
| Age 21 to 24 | 4.8% | 4.9% | 5.2% |
| Age 25 to 34 | 14.7% | 16.5% | 13.8% |
| Age 35 to 44 | 14.3% | 12.3% | 12.9% |
| Age 45 to 54 | 13.2% | 12.4% | 12.6% |
| Age 55 to 59 | 8.0% | 5.7% | 6.7% |
| Age 60 to 64 | 7.5% | 5.1% | 6.3% |
| Age 65 to 74 | 9.4% | 7.5% | 9.6% |
| Age 75 to 84 | 4.8% | 3.1% | 4.5% |
| Age 85 and over | 2.2% | 2.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | San Leandro, CA | Seaside, CA | United States |
| White | 21.5% | 30.5% | 59.4% |
| Black | 9.7% | 7.1% | 12.2% |
| Asian | 34.2% | 9.0% | 5.6% |
| Native American | 0.4% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 1.6% | 2.2% | 0.2% |
| Other | 0.5% | 0.5% | 0.4% |
| Two or More Races | 4.4% | 4.9% | 3.2% |
| Hispanic | 27.6% | 45.7% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | San Leandro, CA | Seaside, CA | United States |
| Married Population | 47.0% | 45.7% | 49.8% |
| Currently Married | 45.3% | 44.5% | 48.0% |
| Married but Separated | 1.7% | 1.2% | 1.8% |
| Single Population | 53.0% | 54.3% | 50.2% |
| Never Married | 38.2% | 40.3% | 33.8% |
| Divorced | 9.9% | 8.8% | 10.8% |
| Widowed | 4.9% | 5.1% | 5.6% |
| space5 | | | |
| Household Size | 2.94 | 3.05 | 2.60 |
| Households | 30,809 | 10,321 | 124,010,992 |
| Family Households | 20,540 | 7,107 | 80,755,759 |
| Married couple, w/children | 30.6% | 34.9% | 30.5% |
| Married couple, no children | 40.5% | 35.6% | 42.9% |
| Non Family Households | 10,269 | 3,214 | 43,255,233 |
| Single householder, w/children | 13.3% | 16.3% | 15.8% |
| Single householder, no children | 15.6% | 13.2% | 10.8% |