| | Niwot, CO | Windsor, CO | United States |
| Population | 4,216 | 31,972 | 329,725,481 |
| Female Population | 52.3% | 49.2% | 50.5% |
| Male Population | 47.7% | 50.8% | 49.5% |
| Median Age | 47.1 | 41.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 3,897 | 18,846 | 309,327,143 |
| Population - 2000 | 4,160 | 9,896 | 285,036,114 |
| Population - 1990 | 2,666 | 5,062 | 251,960,433 |
| Pop. 2000 to Now | 9.8% | 179.5% | 15.6% |
| Pop. 1990 to Now | 71.3% | 446.4% | 30.8% |
| space4 | | | |
| Population Density | 1,054.8 | 1,300.6 | 93.4 |
| Land Area | 4.0 | 24.6 | 3,531,905.4 |
| Water Area | 0.0 | 1.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Niwot, CO | Windsor, CO | United States |
| Age 0 to 4 | 3.0% | 4.3% | 5.9% |
| Age 5 to 9 | 5.2% | 6.6% | 6.1% |
| Age 10 to 14 | 9.1% | 9.9% | 6.6% |
| Age 15 to 17 | 2.8% | 4.9% | 3.9% |
| Age 18 to 20 | 1.1% | 2.0% | 4.0% |
| Age 21 to 24 | 4.5% | 2.8% | 5.2% |
| Age 25 to 34 | 8.6% | 10.0% | 13.8% |
| Age 35 to 44 | 11.3% | 14.1% | 12.9% |
| Age 45 to 54 | 12.2% | 15.8% | 12.6% |
| Age 55 to 59 | 11.3% | 8.3% | 6.7% |
| Age 60 to 64 | 11.4% | 4.7% | 6.3% |
| Age 65 to 74 | 12.0% | 9.7% | 9.6% |
| Age 75 to 84 | 5.6% | 5.5% | 4.5% |
| Age 85 and over | 2.0% | 1.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | Niwot, CO | Windsor, CO | United States |
| White | 93.0% | 86.5% | 59.4% |
| Black | 0.0% | 0.4% | 12.2% |
| Asian | 0.5% | 2.3% | 5.6% |
| Native American | 0.0% | 0.4% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.5% | 0.8% | 0.4% |
| Two or More Races | 0.0% | 1.5% | 3.2% |
| Hispanic | 6.0% | 8.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Niwot, CO | Windsor, CO | United States |
| Married Population | 69.5% | 65.3% | 49.8% |
| Currently Married | 69.5% | 64.4% | 48.0% |
| Married but Separated | 0.0% | 0.9% | 1.8% |
| Single Population | 30.5% | 34.7% | 50.2% |
| Never Married | 19.1% | 20.1% | 33.8% |
| Divorced | 8.6% | 11.1% | 10.8% |
| Widowed | 2.8% | 3.5% | 5.6% |
| space5 | | | |
| Household Size | 2.55 | 2.61 | 2.60 |
| Households | 1,651 | 12,202 | 124,010,992 |
| Family Households | 1,220 | 9,574 | 80,755,759 |
| Married couple, w/children | 37.9% | 36.2% | 30.5% |
| Married couple, no children | 56.2% | 46.8% | 42.9% |
| Non Family Households | 431 | 2,628 | 43,255,233 |
| Single householder, w/children | 4.0% | 10.4% | 15.8% |
| Single householder, no children | 1.9% | 6.6% | 10.8% |