| | Barnwell, SC | Beaufort, SC | United States |
| Population | 4,526 | 12,899 | 329,725,481 |
| Female Population | 56.2% | 52.0% | 50.5% |
| Male Population | 43.8% | 48.0% | 49.5% |
| Median Age | 32.4 | 34.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 4,764 | 12,363 | 309,327,143 |
| Population - 2000 | 5,035 | 12,950 | 285,036,114 |
| Population - 1990 | 5,255 | 9,576 | 251,960,433 |
| Pop. 2000 to Now | -15.4% | 2.0% | 15.6% |
| Pop. 1990 to Now | -18.9% | 37.9% | 30.8% |
| space4 | | | |
| Population Density | 577.2 | 535.6 | 93.4 |
| Land Area | 7.8 | 24.1 | 3,531,905.4 |
| Water Area | 0.1 | 0.9 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Barnwell, SC | Beaufort, SC | United States |
| Age 0 to 4 | 7.9% | 6.7% | 5.9% |
| Age 5 to 9 | 7.4% | 4.4% | 6.1% |
| Age 10 to 14 | 7.4% | 5.7% | 6.6% |
| Age 15 to 17 | 2.5% | 3.8% | 3.9% |
| Age 18 to 20 | 7.4% | 4.5% | 4.0% |
| Age 21 to 24 | 8.4% | 6.3% | 5.2% |
| Age 25 to 34 | 11.8% | 19.0% | 13.8% |
| Age 35 to 44 | 9.4% | 9.9% | 12.9% |
| Age 45 to 54 | 12.3% | 8.5% | 12.6% |
| Age 55 to 59 | 5.0% | 8.8% | 6.7% |
| Age 60 to 64 | 4.9% | 5.8% | 6.3% |
| Age 65 to 74 | 8.0% | 10.4% | 9.6% |
| Age 75 to 84 | 5.2% | 4.7% | 4.5% |
| Age 85 and over | 2.3% | 1.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Barnwell, SC | Beaufort, SC | United States |
| White | 40.9% | 61.9% | 59.4% |
| Black | 57.6% | 30.1% | 12.2% |
| Asian | 0.0% | 0.2% | 5.6% |
| Native American | 0.3% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.4% | 0.1% | 0.4% |
| Two or More Races | 0.4% | 3.4% | 3.2% |
| Hispanic | 0.4% | 4.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Barnwell, SC | Beaufort, SC | United States |
| Married Population | 29.6% | 42.3% | 49.8% |
| Currently Married | 26.3% | 40.3% | 48.0% |
| Married but Separated | 3.3% | 1.9% | 1.8% |
| Single Population | 70.4% | 57.7% | 50.2% |
| Never Married | 49.6% | 39.0% | 33.8% |
| Divorced | 12.0% | 10.4% | 10.8% |
| Widowed | 8.8% | 8.3% | 5.6% |
| space5 | | | |
| Household Size | 2.40 | 2.31 | 2.60 |
| Households | 1,819 | 5,005 | 124,010,992 |
| Family Households | 968 | 3,084 | 80,755,759 |
| Married couple, w/children | 17.7% | 26.6% | 30.5% |
| Married couple, no children | 25.6% | 38.0% | 42.9% |
| Non Family Households | 851 | 1,921 | 43,255,233 |
| Single householder, w/children | 32.0% | 22.1% | 15.8% |
| Single householder, no children | 24.7% | 13.4% | 10.8% |