| County | Rank | Change (2020) ↓ | 2025 Pop. | 2020 Pop. |
|---|---|---|---|---|
| Union County | 1 | 16.78% | 73,677 | 63,090 |
| Delaware County | 2 | 13.03% | 243,200 | 215,162 |
| Pickaway County | 3 | 7.82% | 63,252 | 58,664 |
| Fairfield County | 4 | 6.54% | 169,894 | 159,464 |
| Warren County | 5 | 6.29% | 258,539 | 243,236 |
| Madison County | 6 | 5.78% | 46,394 | 43,858 |
| Licking County | 7 | 4.17% | 186,256 | 178,796 |
| Franklin County | 8 | 3.71% | 1,373,703 | 1,324,505 |
| Miami County | 9 | 3.71% | 113,002 | 108,962 |
| Greene County | 10 | 3.7% | 174,359 | 168,130 |
| Morrow County | 11 | 3.68% | 36,271 | 34,983 |
| Lorain County | 12 | 3.62% | 324,897 | 313,534 |
| Clermont County | 13 | 3.49% | 216,044 | 208,755 |
| Butler County | 14 | 3.22% | 403,491 | 390,887 |
| Knox County | 15 | 2.48% | 64,352 | 62,792 |
| Brown County | 16 | 2.44% | 44,750 | 43,684 |
| Athens County | 17 | 1.74% | 63,467 | 62,380 |
| Portage County | 18 | 1.7% | 164,603 | 161,854 |
| Hamilton County | 19 | 1.53% | 843,159 | 830,418 |
| Defiance County | 20 | 1.53% | 38,851 | 38,267 |
| Holmes County | 21 | 1.49% | 44,897 | 44,236 |
| Coshocton County | 22 | 1.49% | 37,140 | 36,595 |
| Highland County | 23 | 1.43% | 43,982 | 43,364 |
| Medina County | 24 | 1.37% | 185,135 | 182,639 |
| Adams County | 25 | 1.27% | 27,800 | 27,451 |
| Perry County | 26 | 0.94% | 35,787 | 35,455 |
| Wood County | 27 | 0.81% | 133,341 | 132,267 |
| Mercer County | 28 | 0.74% | 42,848 | 42,532 |
| Noble County | 29 | 0.61% | 14,193 | 14,107 |
| Champaign County | 30 | 0.55% | 38,957 | 38,743 |
| Montgomery County | 31 | 0.45% | 539,573 | 537,139 |
| Van Wert County | 32 | 0.45% | 29,049 | 28,919 |
| Muskingum County | 33 | 0.45% | 86,852 | 86,464 |
| Hancock County | 34 | 0.36% | 75,185 | 74,919 |
| Ashland County | 35 | 0.34% | 52,657 | 52,476 |
| Jackson County | 36 | 0.32% | 32,777 | 32,671 |
| Pike County | 37 | 0.26% | 27,147 | 27,076 |
| Stark County | 38 | 0.15% | 375,130 | 374,552 |
| Sandusky County | 39 | 0.12% | 58,947 | 58,878 |
| Lake County | 40 | 0.1% | 232,756 | 232,527 |
| Clinton County | 41 | 0.07% | 42,066 | 42,035 |
| Preble County | 42 | 0.06% | 41,039 | 41,016 |
| Logan County | 43 | 0.02% | 46,125 | 46,114 |
| Summit County | 44 | -0.02% | 539,721 | 539,835 |
| Geauga County | 45 | -0.05% | 95,335 | 95,385 |
| Shelby County | 46 | -0.07% | 48,119 | 48,154 |
| Paulding County | 47 | -0.13% | 18,782 | 18,807 |
| Richland County | 48 | -0.23% | 124,703 | 124,988 |
| Wayne County | 49 | -0.23% | 116,629 | 116,903 |
| Guernsey County | 50 | -0.28% | 38,312 | 38,419 |
| Seneca County | 51 | -0.41% | 54,832 | 55,055 |
| Marion County | 52 | -0.41% | 65,124 | 65,390 |
| Clark County | 53 | -0.48% | 135,235 | 135,894 |
| Henry County | 54 | -0.52% | 27,527 | 27,672 |
| Ashtabula County | 55 | -0.68% | 96,850 | 97,512 |
| Trumbull County | 56 | -0.71% | 200,246 | 201,682 |
| Huron County | 57 | -0.71% | 58,078 | 58,495 |
| Putnam County | 58 | -0.72% | 34,158 | 34,407 |
| Darke County | 59 | -0.78% | 51,492 | 51,897 |
| Crawford County | 60 | -0.84% | 41,661 | 42,015 |
| Fayette County | 61 | -0.85% | 28,733 | 28,978 |
| Lucas County | 62 | -1.05% | 426,342 | 430,870 |
| Hardin County | 63 | -1.05% | 30,398 | 30,722 |
| Mahoning County | 64 | -1.07% | 225,584 | 228,017 |
| Tuscarawas County | 65 | -1.2% | 92,079 | 93,199 |
| Allen County | 66 | -1.23% | 100,881 | 102,137 |
| Fulton County | 67 | -1.25% | 42,105 | 42,640 |
| Auglaize County | 68 | -1.39% | 45,826 | 46,473 |
| Williams County | 69 | -1.46% | 36,542 | 37,084 |
| Gallia County | 70 | -1.48% | 28,808 | 29,240 |
| Cuyahoga County | 71 | -1.59% | 1,242,509 | 1,262,635 |
| Vinton County | 72 | -1.69% | 12,592 | 12,808 |
| Ross County | 73 | -1.71% | 75,752 | 77,068 |
| Ottawa County | 74 | -1.82% | 39,565 | 40,298 |
| Carroll County | 75 | -2.01% | 26,166 | 26,702 |
| Columbiana County | 76 | -2.11% | 99,509 | 101,650 |
| Morgan County | 77 | -2.28% | 13,438 | 13,752 |
| Jefferson County | 78 | -2.3% | 63,684 | 65,186 |
| Wyandot County | 79 | -2.48% | 21,322 | 21,864 |
| Washington County | 80 | -2.52% | 58,151 | 59,656 |
| Erie County | 81 | -2.55% | 73,557 | 75,482 |
| Hocking County | 82 | -2.69% | 27,291 | 28,046 |
| Belmont County | 83 | -2.85% | 64,404 | 66,291 |
| Monroe County | 84 | -3.14% | 12,937 | 13,356 |
| Scioto County | 85 | -3.29% | 71,420 | 73,852 |
| Harrison County | 86 | -4.08% | 13,901 | 14,492 |
| Meigs County | 87 | -4.29% | 21,210 | 22,160 |
| Lawrence County | 88 | -4.51% | 55,520 | 58,141 |
Ohio's counties show varied growth patterns from 2020 to 2025. Union County leads with 16.78% annualized growth, followed by Delaware County (13.03%) and Pickaway County (7.82%). The largest counties are Franklin County (1,373,703), Cuyahoga County (1,242,509), and Hamilton County (843,159). Of the 88 counties in Ohio, 43 are growing while 45 have experienced population decline. Overall, counties averaged 0.5% annualized growth, with total population growing by 1.22% annually.
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