| County | Rank | Change (2020) ↓ | 2025 Pop. | 2020 Pop. |
|---|---|---|---|---|
| Carroll County | 1 | 5.55% | 53,036 | 50,246 |
| Belknap County | 2 | 2.97% | 65,671 | 63,776 |
| Merrimack County | 3 | 2.83% | 158,391 | 154,038 |
| Strafford County | 4 | 2.68% | 134,587 | 131,068 |
| Rockingham County | 5 | 2.6% | 322,801 | 314,621 |
| Sullivan County | 6 | 2.33% | 44,071 | 43,068 |
| Grafton County | 7 | 2.17% | 93,176 | 91,198 |
| Cheshire County | 8 | 2.14% | 78,183 | 76,547 |
| Hillsborough County | 9 | 0.98% | 427,076 | 422,913 |
| Coos County | 10 | -0.2% | 31,164 | 31,227 |
New Hampshire's counties show varied growth patterns from 2020 to 2025. Carroll County leads with 5.55% annualized growth, followed by Belknap County (2.97%) and Merrimack County (2.83%). The largest counties are Hillsborough County (427,076), Rockingham County (322,801), and Merrimack County (158,391). Of the 10 counties in New Hampshire, 9 are growing while 1 has experienced population decline. Overall, counties averaged 2.41% annualized growth, with total population growing by 2.14% annually.