| County | Rank | Change (2020) ↓ | 2026 Pop. | 2020 Pop. |
|---|---|---|---|---|
| Greater Bridgeport Planning Region | 1 | 6.17% | 344,398 | 324,397 |
| Western Connecticut Planning Region | 2 | 5.15% | 650,637 | 618,762 |
| Naugatuck Valley Planning Region | 3 | 4.99% | 471,442 | 449,055 |
| Capitol Planning Region | 4 | 4.54% | 1,007,872 | 964,088 |
| Northeastern Connecticut Planning Region | 5 | 4.41% | 99,435 | 95,231 |
| South Central Connecticut Planning Region | 6 | 3.51% | 584,316 | 564,526 |
| Lower Connecticut River Valley Planning Region | 7 | 3.46% | 179,272 | 173,281 |
| Southeastern Connecticut Planning Region | 8 | 2.94% | 286,562 | 278,379 |
| Northwest Hills Planning Region | 9 | 2.7% | 115,227 | 112,199 |
Connecticut's counties show varied growth patterns from 2020 to 2026. Greater Bridgeport Planning Region leads with 1% annualized growth, followed by Western Connecticut Planning Region (0.84%) and Naugatuck Valley Planning Region (0.81%). The largest counties are Capitol Planning Region (1,007,872), Western Connecticut Planning Region (650,637), and South Central Connecticut Planning Region (584,316). All 9 counties in Connecticut are growing. Overall, counties averaged 0.69% annualized growth, with total population growing by 0.73% annually.
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