Water hardness in Kentucky
Kentucky has a median ambient water hardness of 120 mg/L, which is 7 grains per gallon and classes as moderately hard. That is the middle of 27,861 samples across 120 counties.
This is ambient water, not tap water. These figures come from samples taken from wells, streams and springs by USGS, EPA and state agencies. Municipal utilities treat, blend and sometimes soften water before it reaches a tap, so a city supply can be considerably softer than the ground beneath it. Treat this as a good guide for a private well and an approximate one for city water. Your utility's annual water quality report gives the real number for a municipal tap, and a test strip gives it for yours.
Every monitored county in Kentucky
Ranked hardest first. The middle 50% column shows how much the samples within a county vary, which matters more than the median where a county spans two geologies.
| County | mg/L | gpg | Class | Middle 50% | Samples |
|---|---|---|---|---|---|
| Jefferson County | 470 | 27.5 | Very hard | 270 to 760 | 1,004 |
| McLean County | 461 | 26.9 | Very hard | 216 to 688 | 42 |
| Kenton County | 400 | 23.4 | Very hard | 300 to 600 | 19 |
| Taylor County | 380 | 22.2 | Very hard | 200 to 2,000 | 47 |
| Metcalfe County | 335 | 19.6 | Very hard | 205 to 700 | 84 |
| Carroll County | 330 | 19.3 | Very hard | 300 to 400 | 59 |
| Boone County | 320 | 18.7 | Very hard | 270 to 420 | 23 |
| Nicholas County | 305 | 17.8 | Very hard | 180 to 380 | 6 |
| Trimble County | 300 | 17.5 | Very hard | 235 to 340 | 33 |
| Meade County | 290 | 16.9 | Very hard | 240 to 360 | 217 |
| Campbell County | 280 | 16.4 | Very hard | 151 to 480 | 51 |
| Hopkins County | 279 | 16.3 | Very hard | 120 to 620 | 380 |
| Union County | 262 | 15.3 | Very hard | 179 to 312 | 131 |
| Montgomery County | 260 | 15.2 | Very hard | 220 to 270 | 8 |
| Breathitt County | 253 | 14.8 | Very hard | 145 to 430 | 271 |
| Breckinridge County | 240 | 14 | Very hard | 190 to 330 | 121 |
| Clark County | 240 | 14 | Very hard | 200 to 470 | 14 |
| Fayette County | 240 | 14 | Very hard | 210 to 280 | 170 |
| Mason County | 240 | 14 | Very hard | 170 to 340 | 12 |
| Oldham County | 240 | 14 | Very hard | 211 to 264 | 78 |
| Shelby County | 240 | 14 | Very hard | 180 to 300 | 86 |
| Scott County | 230 | 13.4 | Very hard | 190 to 270 | 81 |
| Anderson County | 226 | 13.2 | Very hard | 199 to 258 | 93 |
| Mercer County | 220 | 12.9 | Very hard | 170 to 220 | 12 |
| Grant County | 216 | 12.6 | Very hard | 184 to 290 | 38 |
| Robertson County | 211 | 12.3 | Very hard | 195 to 241 | 15 |
| Simpson County | 210 | 12.3 | Very hard | 160 to 230 | 36 |
| Woodford County | 210 | 12.3 | Very hard | 189 to 230 | 70 |
| Bourbon County | 208 | 12.2 | Very hard | 185 to 225 | 162 |
| Crittenden County | 208 | 12.2 | Very hard | 172 to 370 | 60 |
| Bracken County | 205 | 12 | Very hard | 180 to 235 | 73 |
| Spencer County | 203 | 11.9 | Very hard | 174 to 222 | 85 |
| Boyle County | 200 | 11.7 | Very hard | 110 to 215 | 5 |
| Christian County | 200 | 11.7 | Very hard | 117 to 236 | 105 |
| Hardin County | 200 | 11.7 | Very hard | 170 to 270 | 505 |
| Bullitt County | 197 | 11.5 | Very hard | 170 to 220 | 493 |
| Washington County | 197 | 11.5 | Very hard | 169 to 233 | 88 |
| Jessamine County | 196 | 11.4 | Very hard | 160 to 260 | 15 |
| Nelson County | 195 | 11.4 | Very hard | 160 to 254 | 109 |
| Caldwell County | 190 | 11.1 | Very hard | 110 to 250 | 678 |
| Todd County | 190 | 11.1 | Very hard | 160 to 220 | 87 |
| Barren County | 186 | 10.9 | Very hard | 157 to 230 | 90 |
| Logan County | 184 | 10.7 | Very hard | 130 to 224 | 174 |
| Daviess County | 180 | 10.5 | Hard | 110 to 310 | 210 |
| Floyd County | 180 | 10.5 | Hard | 115 to 235 | 260 |
| Pike County | 175 | 10.2 | Hard | 96 to 241 | 873 |
| Madison County | 164 | 9.6 | Hard | 123 to 200 | 149 |
| Owen County | 164 | 9.6 | Hard | 143 to 207 | 88 |
| Larue County | 160 | 9.3 | Hard | 136 to 200 | 126 |
| Martin County | 160 | 9.3 | Hard | 86 to 290 | 97 |
| Warren County | 160 | 9.3 | Hard | 130 to 200 | 311 |
| Marion County | 158 | 9.2 | Hard | 144 to 172 | 14 |
| Fulton County | 155 | 9.1 | Hard | 68 to 280 | 82 |
| Grayson County | 155 | 9.1 | Hard | 110 to 200 | 38 |
| Garrard County | 151 | 8.8 | Hard | 130 to 177 | 138 |
| Lincoln County | 151 | 8.8 | Hard | 100 to 290 | 18 |
| Estill County | 150 | 8.8 | Hard | 122 to 251 | 149 |
| Gallatin County | 150 | 8.8 | Hard | 120 to 190 | 636 |
| Perry County | 150 | 8.8 | Hard | 92 to 220 | 297 |
| Bath County | 149 | 8.7 | Hard | 125 to 168 | 97 |
| Trigg County | 149 | 8.7 | Hard | 108 to 190 | 582 |
| Green County | 147 | 8.6 | Hard | 92 to 188 | 416 |
| Leslie County | 145 | 8.5 | Hard | 96 to 187 | 88 |
| Muhlenberg County | 141 | 8.2 | Hard | 90 to 528 | 115 |
| Clinton County | 140 | 8.2 | Hard | 115 to 190 | 141 |
| Hancock County | 140 | 8.2 | Hard | 86 to 290 | 65 |
| Henderson County | 140 | 8.2 | Hard | 100 to 220 | 314 |
| Webster County | 140 | 8.2 | Hard | 120 to 207 | 250 |
| Butler County | 136 | 7.9 | Hard | 111 to 156 | 361 |
| Cumberland County | 136 | 7.9 | Hard | 63 to 170 | 76 |
| Hart County | 130 | 7.6 | Hard | 98 to 160 | 899 |
| Henry County | 130 | 7.6 | Hard | 114 to 157 | 247 |
| Lawrence County | 128 | 7.5 | Hard | 86 to 179 | 391 |
| Allen County | 120 | 7 | Moderately hard | 96 to 140 | 202 |
| Boyd County | 120 | 7 | Moderately hard | 72 to 160 | 266 |
| Franklin County | 110 | 6.4 | Moderately hard | 83 to 151 | 785 |
| Knott County | 110 | 6.4 | Moderately hard | 78 to 150 | 90 |
| Pendleton County | 110 | 6.4 | Moderately hard | 87 to 138 | 782 |
| Greenup County | 109 | 6.4 | Moderately hard | 91 to 133 | 447 |
| Harrison County | 109 | 6.4 | Moderately hard | 93 to 180 | 105 |
| Knox County | 107 | 6.3 | Moderately hard | 78 to 126 | 36 |
| Ohio County | 103 | 6 | Moderately hard | 80 to 131 | 306 |
| Elliott County | 101 | 5.9 | Moderately hard | 87 to 128 | 52 |
| Lee County | 101 | 5.9 | Moderately hard | 72 to 140 | 191 |
| Johnson County | 100 | 5.8 | Moderately hard | 69 to 140 | 182 |
| Clay County | 98 | 5.7 | Moderately hard | 66 to 141 | 158 |
| Wayne County | 98 | 5.7 | Moderately hard | 78 to 188 | 317 |
| Carter County | 97 | 5.7 | Moderately hard | 70 to 134 | 147 |
| Rockcastle County | 97 | 5.7 | Moderately hard | 76 to 125 | 102 |
| Casey County | 96 | 5.6 | Moderately hard | 36 to 100 | 8 |
| Lyon County | 96 | 5.6 | Moderately hard | 84 to 105 | 241 |
| Letcher County | 94 | 5.5 | Moderately hard | 45 to 160 | 162 |
| Fleming County | 92 | 5.4 | Moderately hard | 61 to 290 | 94 |
| Pulaski County | 92 | 5.4 | Moderately hard | 77 to 115 | 550 |
| Edmonson County | 91 | 5.3 | Moderately hard | 72 to 130 | 822 |
| Livingston County | 90 | 5.3 | Moderately hard | 79 to 101 | 402 |
| Powell County | 90 | 5.3 | Moderately hard | 68 to 121 | 105 |
| Morgan County | 88 | 5.1 | Moderately hard | 50 to 114 | 122 |
| Owsley County | 82 | 4.8 | Moderately hard | 59 to 108 | 134 |
| Adair County | 81 | 4.7 | Moderately hard | 70 to 94 | 131 |
| Monroe County | 81 | 4.7 | Moderately hard | 77 to 87 | 74 |
| Jackson County | 80 | 4.7 | Moderately hard | 50 to 113 | 118 |
| Russell County | 77 | 4.5 | Moderately hard | 72 to 83 | 200 |
| Rowan County | 75 | 4.4 | Moderately hard | 54 to 105 | 38 |
| Whitley County | 73 | 4.3 | Moderately hard | 57 to 92 | 813 |
| Laurel County | 72 | 4.2 | Moderately hard | 58 to 100 | 429 |
| McCracken County | 64 | 3.7 | Moderately hard | 54 to 72 | 527 |
| McCreary County | 64 | 3.7 | Moderately hard | 35 to 110 | 935 |
| Ballard County | 63 | 3.7 | Moderately hard | 38 to 86 | 76 |
| Marshall County | 62 | 3.6 | Moderately hard | 48 to 77 | 338 |
| Menifee County | 62 | 3.6 | Moderately hard | 48 to 76 | 65 |
| Harlan County | 59 | 3.4 | Soft | 49 to 110 | 691 |
| Magoffin County | 55 | 3.2 | Soft | 32 to 85 | 115 |
| Bell County | 49 | 2.9 | Soft | 25 to 92 | 1,986 |
| Lewis County | 47 | 2.7 | Soft | 35 to 130 | 104 |
| Wolfe County | 45 | 2.6 | Soft | 30 to 55 | 93 |
| Carlisle County | 34 | 2 | Soft | 24 to 43 | 160 |
| Hickman County | 34 | 2 | Soft | 27 to 41 | 165 |
| Calloway County | 31 | 1.8 | Soft | 19 to 46 | 225 |
| Graves County | 24 | 1.4 | Soft | 14 to 33 | 312 |
Source: Water Quality Portal (USGS, EPA and state agencies), waterqualitydata.us, retrieved 2026-09-19. 2,904,346 samples across 3,110 counties.
What this means for a household in Kentucky
At 7 grains per gallon, a family of four would need a softener of about 16,000 grains to regenerate roughly weekly, using around 288 lb of salt a year. Size it for your own household.
117 of these counties include well samples, so the figures are a reasonable guide for private well water there. Municipal supplies in the same counties may be softer, because utilities often blend or treat.
Hardness follows geology rather than borders. Where a county sits on limestone or dolomite the water is hard; on granite, basalt or sandstone it is soft. That is why neighbouring counties in this table can differ by a factor of several.