Water hardness in Michigan
Michigan has a median ambient water hardness of 168 mg/L, which is 9.8 grains per gallon and classes as hard. That is the middle of 21,436 samples across 83 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 Michigan
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 |
|---|---|---|---|---|---|
| Gratiot County | 352 | 20.6 | Very hard | 260 to 471 | 24 |
| Huron County | 352 | 20.6 | Very hard | 263 to 430 | 182 |
| Isabella County | 345 | 20.2 | Very hard | 206 to 563 | 26 |
| Sanilac County | 340 | 19.9 | Very hard | 244 to 440 | 79 |
| Ingham County | 324 | 18.9 | Very hard | 270 to 400 | 287 |
| Eaton County | 322 | 18.8 | Very hard | 290 to 380 | 114 |
| Lenawee County | 320 | 18.7 | Very hard | 284 to 360 | 88 |
| Monroe County | 318 | 18.6 | Very hard | 270 to 370 | 416 |
| Clinton County | 300 | 17.5 | Very hard | 260 to 355 | 208 |
| Shiawassee County | 295 | 17.2 | Very hard | 250 to 340 | 34 |
| Ionia County | 290 | 16.9 | Very hard | 260 to 310 | 125 |
| Lapeer County | 286 | 16.7 | Very hard | 251 to 350 | 86 |
| Hillsdale County | 280 | 16.4 | Very hard | 250 to 310 | 110 |
| Washtenaw County | 280 | 16.4 | Very hard | 240 to 349 | 698 |
| Livingston County | 277 | 16.2 | Very hard | 230 to 380 | 191 |
| Branch County | 270 | 15.8 | Very hard | 240 to 330 | 175 |
| Calhoun County | 270 | 15.8 | Very hard | 200 to 300 | 57 |
| Oakland County | 270 | 15.8 | Very hard | 226 to 320 | 941 |
| Macomb County | 266 | 15.5 | Very hard | 240 to 290 | 826 |
| Berrien County | 260 | 15.2 | Very hard | 250 to 274 | 259 |
| Jackson County | 260 | 15.2 | Very hard | 220 to 316 | 106 |
| Kalamazoo County | 260 | 15.2 | Very hard | 220 to 300 | 528 |
| Ottawa County | 260 | 15.2 | Very hard | 230 to 280 | 389 |
| Saginaw County | 260 | 15.2 | Very hard | 230 to 290 | 612 |
| Allegan County | 250 | 14.6 | Very hard | 230 to 260 | 436 |
| St. Joseph County | 250 | 14.6 | Very hard | 230 to 260 | 98 |
| Midland County | 248 | 14.5 | Very hard | 219 to 280 | 85 |
| Bay County | 240 | 14 | Very hard | 220 to 270 | 200 |
| Kent County | 240 | 14 | Very hard | 180 to 316 | 43 |
| Tuscola County | 230 | 13.4 | Very hard | 184 to 297 | 33 |
| Cass County | 220 | 12.9 | Very hard | 180 to 262 | 35 |
| Genesee County | 220 | 12.9 | Very hard | 170 to 270 | 112 |
| Menominee County | 220 | 12.9 | Very hard | 170 to 260 | 630 |
| Arenac County | 210 | 12.3 | Very hard | 190 to 220 | 177 |
| Barry County | 200 | 11.7 | Very hard | 160 to 280 | 47 |
| Gladwin County | 200 | 11.7 | Very hard | 160 to 342 | 34 |
| Montmorency County | 190 | 11.1 | Very hard | 140 to 200 | 30 |
| Otsego County | 190 | 11.1 | Very hard | 140 to 200 | 49 |
| Oscoda County | 186 | 10.9 | Very hard | 140 to 200 | 21 |
| Alpena County | 180 | 10.5 | Hard | 170 to 195 | 195 |
| Antrim County | 170 | 9.9 | Hard | 150 to 180 | 22 |
| Emmet County | 170 | 9.9 | Hard | 140 to 180 | 9 |
| Montcalm County | 170 | 9.9 | Hard | 140 to 240 | 37 |
| Manistee County | 164 | 9.6 | Hard | 152 to 172 | 2,341 |
| Cheboygan County | 160 | 9.3 | Hard | 150 to 170 | 238 |
| Grand Traverse County | 160 | 9.3 | Hard | 140 to 180 | 193 |
| Lake County | 160 | 9.3 | Hard | 120 to 160 | 37 |
| Leelanau County | 160 | 9.3 | Hard | 130 to 180 | 68 |
| Mason County | 160 | 9.3 | Hard | 130 to 170 | 175 |
| Muskegon County | 160 | 9.3 | Hard | 150 to 180 | 97 |
| Newaygo County | 160 | 9.3 | Hard | 150 to 180 | 355 |
| Oceana County | 160 | 9.3 | Hard | 145 to 180 | 17 |
| Ogemaw County | 160 | 9.3 | Hard | 130 to 200 | 42 |
| Osceola County | 160 | 9.3 | Hard | 120 to 170 | 91 |
| Benzie County | 150 | 8.8 | Hard | 140 to 170 | 46 |
| Charlevoix County | 150 | 8.8 | Hard | 140 to 170 | 11 |
| Crawford County | 150 | 8.8 | Hard | 130 to 160 | 53 |
| Iosco County | 150 | 8.8 | Hard | 140 to 160 | 343 |
| Van Buren County | 150 | 8.8 | Hard | 100 to 210 | 217 |
| Wexford County | 150 | 8.8 | Hard | 96 to 210 | 25 |
| Presque Isle County | 145 | 8.5 | Hard | 92 to 160 | 16 |
| Mecosta County | 140 | 8.2 | Hard | 130 to 170 | 27 |
| Missaukee County | 132 | 7.7 | Hard | 72 to 173 | 11 |
| Delta County | 130 | 7.6 | Hard | 98 to 194 | 715 |
| Alcona County | 120 | 7 | Moderately hard | 120 to 130 | 10 |
| Clare County | 120 | 7 | Moderately hard | 83 to 182 | 23 |
| Roscommon County | 120 | 7 | Moderately hard | 90 to 154 | 12 |
| Wayne County | 110 | 6.4 | Moderately hard | 98 to 290 | 645 |
| Kalkaska County | 105 | 6.1 | Moderately hard | 79 to 137 | 16 |
| Mackinac County | 100 | 5.8 | Moderately hard | 87 to 120 | 85 |
| St. Clair County | 100 | 5.8 | Moderately hard | 96 to 280 | 529 |
| Alger County | 93 | 5.4 | Moderately hard | 58 to 142 | 168 |
| Schoolcraft County | 91 | 5.3 | Moderately hard | 69 to 100 | 322 |
| Iron County | 73 | 4.3 | Moderately hard | 40 to 110 | 56 |
| Luce County | 72 | 4.2 | Moderately hard | 51 to 82 | 154 |
| Houghton County | 67 | 3.9 | Moderately hard | 46 to 82 | 130 |
| Keweenaw County | 67 | 3.9 | Moderately hard | 48 to 82 | 227 |
| Ontonagon County | 65 | 3.8 | Moderately hard | 51 to 78 | 327 |
| Marquette County | 60 | 3.5 | Soft | 34 to 88 | 1,280 |
| Dickinson County | 53 | 3.1 | Soft | 40 to 130 | 191 |
| Baraga County | 50 | 2.9 | Soft | 37 to 85 | 1,777 |
| Chippewa County | 48 | 2.8 | Soft | 40 to 60 | 1,408 |
| Gogebic County | 48 | 2.8 | Soft | 34 to 72 | 104 |
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 Michigan
At 9.8 grains per gallon, a family of four would need a softener of about 24,000 grains to regenerate roughly weekly, using around 403 lb of salt a year. Size it for your own household.
82 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.