Water hardness by state

Median hardness of all ambient water samples recorded in each state, with the county breakdown behind each one. States vary enormously internally, so the county page is the more useful number.

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.

Median ambient water hardness by state
State	mg/L	gpg	Class	Counties	Samples
Alabama	49	2.9	Soft	67	55,075
Alaska	70	4.1	Moderately hard	27	15,903
Arizona	310	18.1	Very hard	15	57,699
Arkansas	62	3.6	Moderately hard	75	96,554
California	156	9.1	Hard	58	107,626
Colorado	160	9.3	Hard	64	225,747
Connecticut	44	2.6	Soft	8	19,758
Delaware	70	4.1	Moderately hard	3	44,424
Florida	160	9.3	Hard	67	152,658
Georgia	25	1.5	Soft	159	96,276
Hawaii	38	2.2	Soft	5	3,131
Idaho	130	7.6	Hard	44	33,816
Illinois	285	16.6	Very hard	102	77,575
Indiana	280	16.4	Very hard	92	31,856
Iowa	310	18.1	Very hard	99	22,933
Kansas	260	15.2	Very hard	105	104,519
Kentucky	120	7	Moderately hard	120	27,861
Louisiana	92	5.4	Moderately hard	64	83,426
Maine	17	1	Soft	15	3,535
Maryland	59	3.4	Soft	24	15,744
Massachusetts	44	2.6	Soft	14	10,424
Michigan	168	9.8	Hard	83	21,436
Minnesota	140	8.2	Hard	87	63,339
Mississippi	21	1.2	Soft	82	11,461
Missouri	197	11.5	Very hard	115	36,787
Montana	210	12.3	Very hard	56	88,640
Nebraska	233	13.6	Very hard	93	24,595
Nevada	133	7.8	Hard	17	24,625
New Hampshire	22	1.3	Soft	10	5,064
New Jersey	60	3.5	Soft	21	44,734
New Mexico	224	13.1	Very hard	33	44,023
New York	26	1.5	Soft	62	85,342
North Carolina	28	1.6	Soft	100	80,517
North Dakota	314	18.3	Very hard	53	50,666
Ohio	271	15.8	Very hard	88	93,627
Oklahoma	270	15.8	Very hard	77	97,888
Oregon	50	2.9	Soft	36	54,035
Pennsylvania	83	4.8	Moderately hard	67	126,184
Rhode Island	21	1.2	Soft	5	2,518
South Carolina	19	1.1	Soft	46	32,920
South Dakota	403	23.5	Very hard	66	54,835
Tennessee	78	4.6	Moderately hard	95	49,820
Texas	190	11.1	Very hard	234	144,208
Utah	272	15.9	Very hard	29	139,440
Vermont	46	2.7	Soft	14	11,588
Virginia	41	2.4	Soft	124	53,025
Washington	32	1.9	Soft	39	84,140
West Virginia	77	4.5	Moderately hard	55	12,899
Wisconsin	110	6.4	Moderately hard	72	33,118
Wyoming	248	14.5	Very hard	23	46,181

Source: Water Quality Portal (USGS, EPA and state agencies), waterqualitydata.us, retrieved 2026-09-19. 2,904,346 samples across 3,110 counties.

Frequently asked questions

Which US state has the hardest water?

By median ambient sample, South Dakota at 403 mg/L (23.5 gpg), North Dakota at 314 mg/L (18.3 gpg), Arizona at 310 mg/L (18.1 gpg). State medians hide a lot of variation, so the county figures are more useful.

Which state has the softest water?

By median ambient sample, Maine at 17 mg/L (1 gpg), South Carolina at 19 mg/L (1.1 gpg), Mississippi at 21 mg/L (1.2 gpg). Soft water tends to follow granite and volcanic geology rather than limestone.

Why does water hardness vary so much within one state?

Because hardness comes from the rock the water moves through. Limestone and dolomite dissolve readily and produce hard water; granite, basalt and sandstone produce soft water. A state spanning both geologies has both, which is why the county figure matters more than the state one.

Water hardness by state

Frequently asked questions

Related tools

Hardness by county

The hardness scale

Cookies on this site