| | Winchester, MA | Belmont, MA | United States |
| Population | 22,875 | 27,056 | 329,725,481 |
| Female Population | 53.6% | 52.8% | 50.5% |
| Male Population | 46.4% | 47.2% | 49.5% |
| Median Age | 42.4 | 41.5 | 38.4 |
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| Population - 2010 | 21,473 | 24,700 | 309,327,143 |
| Population - 2000 | 20,810 | 24,194 | 285,036,114 |
| Population - 1990 | 20,267 | 24,720 | 251,960,433 |
| Pop. 2000 to Now | 9.0% | 6.9% | 15.6% |
| Pop. 1990 to Now | 11.9% | 4.7% | 30.8% |
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| Population Density | 3,792.9 | 5,817.2 | 93.4 |
| Land Area | 6.0 | 4.7 | 3,531,905.4 |
| Water Area | 0.3 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Winchester, MA | Belmont, MA | United States |
| Age 0 to 4 | 5.7% | 6.3% | 5.9% |
| Age 5 to 9 | 8.0% | 7.3% | 6.1% |
| Age 10 to 14 | 8.8% | 6.1% | 6.6% |
| Age 15 to 17 | 5.2% | 5.0% | 3.9% |
| Age 18 to 20 | 2.6% | 2.3% | 4.0% |
| Age 21 to 24 | 2.4% | 2.9% | 5.2% |
| Age 25 to 34 | 6.8% | 9.8% | 13.8% |
| Age 35 to 44 | 13.8% | 15.3% | 12.9% |
| Age 45 to 54 | 17.6% | 15.1% | 12.6% |
| Age 55 to 59 | 7.2% | 7.0% | 6.7% |
| Age 60 to 64 | 4.3% | 5.6% | 6.3% |
| Age 65 to 74 | 8.4% | 10.0% | 9.6% |
| Age 75 to 84 | 5.6% | 5.0% | 4.5% |
| Age 85 and over | 3.6% | 2.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | Winchester, MA | Belmont, MA | United States |
| White | 75.4% | 72.5% | 59.4% |
| Black | 1.8% | 1.2% | 12.2% |
| Asian | 15.2% | 18.2% | 5.6% |
| Native American | 0.3% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 1.6% | 0.1% | 0.4% |
| Two or More Races | 3.6% | 3.9% | 3.2% |
| Hispanic | 2.1% | 4.2% | 18.4% |
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| Marriage & Family | | | |
| | Winchester, MA | Belmont, MA | United States |
| Married Population | 62.2% | 64.4% | 49.8% |
| Currently Married | 61.7% | 63.6% | 48.0% |
| Married but Separated | 0.6% | 0.9% | 1.8% |
| Single Population | 37.8% | 35.6% | 50.2% |
| Never Married | 24.1% | 24.7% | 33.8% |
| Divorced | 7.5% | 5.6% | 10.8% |
| Widowed | 6.2% | 5.3% | 5.6% |
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| Household Size | 2.77 | 2.58 | 2.60 |
| Households | 8,149 | 10,393 | 124,010,992 |
| Family Households | 5,980 | 7,556 | 80,755,759 |
| Married couple, w/children | 48.3% | 45.1% | 30.5% |
| Married couple, no children | 37.7% | 41.5% | 42.9% |
| Non Family Households | 2,169 | 2,837 | 43,255,233 |
| Single householder, w/children | 8.2% | 7.7% | 15.8% |
| Single householder, no children | 5.7% | 5.8% | 10.8% |