| | Claremont, CA | Diamond Bar, CA | United States |
| Population | 36,312 | 55,339 | 329,725,481 |
| Female Population | 52.6% | 51.7% | 50.5% |
| Male Population | 47.4% | 48.3% | 49.5% |
| Median Age | 41.3 | 43.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 34,877 | 55,559 | 309,327,143 |
| Population - 2000 | 33,998 | 56,287 | 285,036,114 |
| Population - 1990 | 32,503 | 53,672 | 251,960,433 |
| Pop. 2000 to Now | 3.2% | -2.5% | 15.6% |
| Pop. 1990 to Now | 8.0% | 2.3% | 30.8% |
| space4 | | | |
| Population Density | 2,719.6 | 3,721.5 | 93.4 |
| Land Area | 13.4 | 14.9 | 3,531,905.4 |
| Water Area | 0.1 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Claremont, CA | Diamond Bar, CA | United States |
| Age 0 to 4 | 3.8% | 5.3% | 5.9% |
| Age 5 to 9 | 3.9% | 5.4% | 6.1% |
| Age 10 to 14 | 6.8% | 6.2% | 6.6% |
| Age 15 to 17 | 3.1% | 3.4% | 3.9% |
| Age 18 to 20 | 10.3% | 2.8% | 4.0% |
| Age 21 to 24 | 5.8% | 4.1% | 5.2% |
| Age 25 to 34 | 9.2% | 12.1% | 13.8% |
| Age 35 to 44 | 11.5% | 12.4% | 12.9% |
| Age 45 to 54 | 13.2% | 14.6% | 12.6% |
| Age 55 to 59 | 6.0% | 8.2% | 6.7% |
| Age 60 to 64 | 6.5% | 7.2% | 6.3% |
| Age 65 to 74 | 10.7% | 12.6% | 9.6% |
| Age 75 to 84 | 6.0% | 4.0% | 4.5% |
| Age 85 and over | 3.3% | 1.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Claremont, CA | Diamond Bar, CA | United States |
| White | 47.4% | 14.1% | 59.4% |
| Black | 5.6% | 4.0% | 12.2% |
| Asian | 15.3% | 60.7% | 5.6% |
| Native American | 0.2% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.2% | 0.2% | 0.2% |
| Other | 0.7% | 0.4% | 0.4% |
| Two or More Races | 6.7% | 2.7% | 3.2% |
| Hispanic | 23.9% | 17.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Claremont, CA | Diamond Bar, CA | United States |
| Married Population | 48.2% | 57.8% | 49.8% |
| Currently Married | 47.4% | 57.2% | 48.0% |
| Married but Separated | 0.8% | 0.7% | 1.8% |
| Single Population | 51.8% | 42.2% | 50.2% |
| Never Married | 37.0% | 29.5% | 33.8% |
| Divorced | 9.2% | 7.6% | 10.8% |
| Widowed | 5.6% | 5.1% | 5.6% |
| space5 | | | |
| Household Size | 2.63 | 3.10 | 2.60 |
| Households | 12,172 | 17,788 | 124,010,992 |
| Family Households | 8,669 | 14,446 | 80,755,759 |
| Married couple, w/children | 29.5% | 32.0% | 30.5% |
| Married couple, no children | 50.3% | 47.1% | 42.9% |
| Non Family Households | 3,503 | 3,342 | 43,255,233 |
| Single householder, w/children | 8.6% | 8.7% | 15.8% |
| Single householder, no children | 11.7% | 12.2% | 10.8% |