| | New Marlborough, MA | Belchertown, MA | United States |
| Population | 1,573 | 15,228 | 329,725,481 |
| Female Population | 53.3% | 49.8% | 50.5% |
| Male Population | 46.7% | 50.2% | 49.5% |
| Median Age | 51.2 | 42.8 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,512 | 14,661 | 309,327,143 |
| Population - 2000 | 1,494 | 12,968 | 285,036,114 |
| Population - 1990 | 1,240 | 10,579 | 251,960,433 |
| Pop. 2000 to Now | -3.0% | 16.5% | 15.6% |
| Pop. 1990 to Now | 16.9% | 42.8% | 30.8% |
| space4 | | | |
| Population Density | 33.6 | 289.3 | 93.4 |
| Land Area | 46.9 | 52.6 | 3,531,905.4 |
| Water Area | 1.0 | 2.7 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | New Marlborough, MA | Belchertown, MA | United States |
| Age 0 to 4 | 3.3% | 5.8% | 5.9% |
| Age 5 to 9 | 5.4% | 4.4% | 6.1% |
| Age 10 to 14 | 4.8% | 7.2% | 6.6% |
| Age 15 to 17 | 6.0% | 3.1% | 3.9% |
| Age 18 to 20 | 3.8% | 3.6% | 4.0% |
| Age 21 to 24 | 3.0% | 5.5% | 5.2% |
| Age 25 to 34 | 4.1% | 10.4% | 13.8% |
| Age 35 to 44 | 13.0% | 13.6% | 12.9% |
| Age 45 to 54 | 15.6% | 14.5% | 12.6% |
| Age 55 to 59 | 9.3% | 5.8% | 6.7% |
| Age 60 to 64 | 6.9% | 9.6% | 6.3% |
| Age 65 to 74 | 13.5% | 11.4% | 9.6% |
| Age 75 to 84 | 8.5% | 3.8% | 4.5% |
| Age 85 and over | 2.7% | 1.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | New Marlborough, MA | Belchertown, MA | United States |
| White | 89.3% | 89.5% | 59.4% |
| Black | 2.5% | 0.3% | 12.2% |
| Asian | 0.6% | 3.2% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.2% | 0.0% | 0.2% |
| Other | 0.0% | 1.1% | 0.4% |
| Two or More Races | 0.5% | 1.8% | 3.2% |
| Hispanic | 6.9% | 4.1% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | New Marlborough, MA | Belchertown, MA | United States |
| Married Population | 59.3% | 59.8% | 49.8% |
| Currently Married | 57.3% | 58.9% | 48.0% |
| Married but Separated | 2.0% | 0.9% | 1.8% |
| Single Population | 40.7% | 40.2% | 50.2% |
| Never Married | 28.3% | 28.0% | 33.8% |
| Divorced | 9.3% | 7.5% | 10.8% |
| Widowed | 3.1% | 4.7% | 5.6% |
| space5 | | | |
| Household Size | 2.41 | 2.59 | 2.60 |
| Households | 652 | 5,888 | 124,010,992 |
| Family Households | 446 | 4,238 | 80,755,759 |
| Married couple, w/children | 22.2% | 32.4% | 30.5% |
| Married couple, no children | 62.6% | 48.6% | 42.9% |
| Non Family Households | 206 | 1,650 | 43,255,233 |
| Single householder, w/children | 11.0% | 6.6% | 15.8% |
| Single householder, no children | 4.3% | 12.4% | 10.8% |