| | Amherst, NH | Petersham, MA | United States |
| Population | 11,712 | 1,141 | 329,725,481 |
| Female Population | 50.9% | 45.8% | 50.5% |
| Male Population | 49.1% | 54.2% | 49.5% |
| Median Age | 46.7 | 51.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 11,204 | 1,236 | 309,327,143 |
| Population - 2000 | 10,769 | 1,180 | 285,036,114 |
| Population - 1990 | 9,068 | 1,131 | 251,960,433 |
| Pop. 2000 to Now | 6.0% | 4.8% | 15.6% |
| Pop. 1990 to Now | 25.9% | 9.4% | 30.8% |
| space4 | | | |
| Population Density | 342.6 | 21.0 | 93.4 |
| Land Area | 34.2 | 54.2 | 3,531,905.4 |
| Water Area | 0.5 | 14.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Amherst, NH | Petersham, MA | United States |
| Age 0 to 4 | 5.6% | 2.0% | 5.9% |
| Age 5 to 9 | 5.7% | 6.3% | 6.1% |
| Age 10 to 14 | 7.0% | 3.8% | 6.6% |
| Age 15 to 17 | 4.2% | 1.8% | 3.9% |
| Age 18 to 20 | 3.7% | 5.2% | 4.0% |
| Age 21 to 24 | 2.1% | 4.2% | 5.2% |
| Age 25 to 34 | 8.1% | 6.5% | 13.8% |
| Age 35 to 44 | 12.0% | 8.7% | 12.9% |
| Age 45 to 54 | 15.0% | 16.3% | 12.6% |
| Age 55 to 59 | 7.7% | 8.6% | 6.7% |
| Age 60 to 64 | 10.7% | 9.7% | 6.3% |
| Age 65 to 74 | 12.6% | 17.9% | 9.6% |
| Age 75 to 84 | 3.6% | 4.4% | 4.5% |
| Age 85 and over | 1.9% | 4.7% | 1.9% |
| space1 | | | |
| Race | | | |
| | Amherst, NH | Petersham, MA | United States |
| White | 93.8% | 89.8% | 59.4% |
| Black | 0.0% | 0.0% | 12.2% |
| Asian | 1.6% | 1.0% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.3% | 0.2% |
| Other | 0.0% | 0.4% | 0.4% |
| Two or More Races | 1.7% | 4.8% | 3.2% |
| Hispanic | 2.9% | 3.7% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Amherst, NH | Petersham, MA | United States |
| Married Population | 68.8% | 56.0% | 49.8% |
| Currently Married | 67.8% | 55.6% | 48.0% |
| Married but Separated | 1.1% | 0.4% | 1.8% |
| Single Population | 31.2% | 44.0% | 50.2% |
| Never Married | 18.6% | 27.3% | 33.8% |
| Divorced | 7.6% | 8.6% | 10.8% |
| Widowed | 4.9% | 8.1% | 5.6% |
| space5 | | | |
| Household Size | 2.64 | 2.32 | 2.60 |
| Households | 4,438 | 458 | 124,010,992 |
| Family Households | 3,405 | 299 | 80,755,759 |
| Married couple, w/children | 37.0% | 28.8% | 30.5% |
| Married couple, no children | 54.1% | 58.5% | 42.9% |
| Non Family Households | 1,033 | 159 | 43,255,233 |
| Single householder, w/children | 4.3% | 3.3% | 15.8% |
| Single householder, no children | 4.5% | 9.4% | 10.8% |