What is the US national average for water hardness?

The US national average water hardness is approximately 7 GPG (120 PPM), which falls at the boundary between "Moderately Hard" and "Hard." About half of US states exceed this average, primarily in the Southwest, Midwest, and Great Plains regions.

Why do state averages vary so much?

State water hardness depends on geology and water sources. States with limestone, dolomite, and sedimentary rock (Southwest, Midwest) have very hard water. States with granite and volcanic rock (Pacific Northwest, New England) have naturally soft water. Climate also matters — arid states concentrate minerals through evaporation.

How accurate are state averages?

State averages provide useful context but can mask significant city-level variation. For example, California averages 11.7 GPG, but San Francisco is only 1.5 GPG while Los Angeles exceeds 15 GPG. For treatment decisions, always check your specific city or ZIP code.

Which states definitely need water softeners?

States averaging above 10.5 GPG (Very Hard) would benefit most from water softeners: Nevada (17.5), Indiana (17.4), Arizona (16.4), Texas (15.7), Utah (15.1), New Mexico (14.7), Kansas (14.6), Nebraska (12.3), Oklahoma (12.3), Wyoming (12.3), California (11.7), Delaware (11.7), Florida (11.7), Missouri (11.7), and Colorado (10.8).

Which states have water soft enough that no treatment is needed?

States below 3.5 GPG rarely need any water treatment for hardness: Arkansas (2.2 GPG), Massachusetts (2.9 GPG), Hawaii (3.5 GPG), Maine (3.5 GPG), and New Hampshire (3.5 GPG). Many cities in these states have water below 1 GPG.

Water Hardness by State: All 50 States Ranked

Average water hardness for every US state, ranked from hardest to softest. Data from USGS and EPA sources, updated for 2026.

Quick Reference

US Average: ~7 GPG (120 PPM)

Hardest state: Nevada (17.5 GPG)

Softest state: Arkansas (2.2 GPG)

Soft (0–1 GPG)

Slightly Hard (1–3.5 GPG)

Moderately Hard (3.5–7 GPG)

Hard (7–10.5 GPG)

Very Hard (10.5–25+ GPG)

Rank	State	Avg GPG	Avg PPM	Level	Primary Sources
1	Nevada Las Vegas Henderson North Las Vegas Boulder City	17.5	300	Very Hard	Surface (L. Mead) and Groundwater
2	Indiana	17.4	298	Very Hard	Groundwater and Surface Blends
3	Arizona Phoenix Scottsdale Mesa Tempe Chandler Gilbert Glendale Peoria	16.4	280	Very Hard	Surface (Colorado R.) and Groundwater
4	Texas	15.7	268	Very Hard	Surface and Groundwater
5	Utah	15.1	259	Very Hard	Surface and Groundwater
6	New Mexico	14.7	252	Very Hard	Groundwater and Surface
7	Kansas	14.6	250	Very Hard	Groundwater (Ogallala/High Plains)
8	Nebraska	12.3	210	Very Hard	Groundwater (Ogallala)
9	Oklahoma	12.3	210	Very Hard	Surface and Groundwater
10	Wyoming	12.3	210	Very Hard	Surface and Groundwater
11	California	11.7	200	Very Hard	Surface (SWP) and Groundwater
12	Delaware	11.7	200	Very Hard	Groundwater (94% reliance)
13	Florida	11.7	200	Very Hard	Groundwater (Floridan Aquifer)
14	Missouri	11.7	200	Very Hard	Surface (Missouri R.) and Ground
15	Colorado	10.8	185	Very Hard	Surface (Snowmelt) and Groundwater
16	Minnesota	10.2	175	Hard	Surface (Mississippi) and Groundwater
17	Alabama	8.8	150	Hard	Surface and Groundwater
18	South Dakota	8.8	150	Hard	Surface and Groundwater
19	Michigan	8.2	140	Hard	Surface (Lakes) and Groundwater
20	Wisconsin	8.2	140	Hard	Surface and Groundwater
21	District of Columbia	7.9	135	Hard	Surface (Potomac River)
22	Georgia	7.6	130	Hard	Surface and Groundwater
23	Iowa	7.6	130	Hard	Groundwater (75% reliance)
24	North Dakota	7.6	130	Hard	Surface and Groundwater
25	Ohio	7.6	130	Hard	Surface and Groundwater
26	South Carolina	7.6	130	Hard	Surface and Groundwater
27	Tennessee	7.6	130	Hard	Surface and Groundwater
28	West Virginia	7.6	130	Hard	Surface and Groundwater
29	Illinois	7	120	Hard	Surface (L. Michigan) and Groundwater
30	North Carolina	7	120	Hard	Surface and Groundwater
31	Pennsylvania	7	120	Hard	Surface and Groundwater
32	Virginia	7	120	Hard	Surface and Groundwater
33	Maryland	6.9	118	Moderately Hard	Surface and Groundwater
34	Kentucky	6.5	112	Moderately Hard	Surface (Ohio River) and Groundwater
35	Alaska	5.8	100	Moderately Hard	Surface and Groundwater
36	Idaho	5.8	100	Moderately Hard	Surface and Snake River Aquifer
37	Louisiana	5.8	100	Moderately Hard	Surface and Groundwater
38	New Jersey	5.8	100	Moderately Hard	Surface and Groundwater
39	Montana	5.6	95	Moderately Hard	Surface and Groundwater
40	Connecticut	4.4	75	Moderately Hard	Surface and Bedrock Wells
41	New York	4.4	75	Moderately Hard	Surface Reservoirs
42	Rhode Island	4.4	75	Moderately Hard	Surface Reservoirs
43	Mississippi	4.1	70	Moderately Hard	Groundwater (84% reliance)
44	Oregon	4.1	70	Moderately Hard	Surface (Columbia/Willamette)
45	Vermont	4.1	70	Moderately Hard	Surface and Bedrock Wells
46	Washington	4.1	70	Moderately Hard	Surface (Cedar/Tolt Rivers)
47	Hawaii	3.5	60	Moderately Hard	Groundwater (Volcanic)
48	Maine	3.5	60	Moderately Hard	Surface (Lakes) and Bedrock Wells
49	New Hampshire	3.5	60	Moderately Hard	Surface and Groundwater
50	Massachusetts	2.9	50	Slightly Hard	Surface (Quabbin Reservoir)
51	Arkansas	2.2	38	Slightly Hard	Surface (Reservoirs/Rivers)

Regional Water Hardness Patterns

Southwest (NV, AZ, NM, UT, TX)

The hardest water in the US. These states draw from the Colorado River system and arid basin aquifers that flow through extensive limestone and dolomite formations. The desert climate concentrates minerals through evaporation, pushing averages above 15 GPG. Nearly every household would benefit from a water softener.

Great Plains & Midwest (IN, KS, NE, OK, WY, MO)

The Ogallala Aquifer and glacial limestone deposits drive very hard water across the heartland. Indiana leads with 17.4 GPG due to Paleozoic-era limestone crushed and redistributed by glaciers. States relying on the High Plains aquifer typically exceed 12 GPG.

Southeast (FL, GA, AL, SC, TN)

A mixed region. Florida's Floridan Aquifer produces very hard water (11.7 GPG) from its limestone composition. Other southeastern states range from moderately hard to hard, with softer water in mountainous areas and harder water in coastal plains.

New England (MA, ME, NH, VT, CT, RI)

Naturally soft water from crystalline bedrock (granite and metamorphic rock) that doesn't dissolve calcium or magnesium. Protected reservoir systems like Massachusetts' Quabbin Reservoir deliver some of the softest municipal water in the country. Most residents need no water treatment.

Pacific Northwest (OR, WA)

Mountain snowmelt and rain flowing through volcanic basalt produce consistently soft water. Portland (0.5 GPG) and Seattle (1.2 GPG) have some of the softest city water in the US, though Eastern Washington and Oregon's high desert regions are notably harder.

Check Your Water Hardness

State averages are a starting point. Enter your ZIP code for city-level data and personalized recommendations.

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Frequently Asked Questions

State averages synthesized from USGS groundwater studies, EPA SDWIS records, and state environmental reports. GPG values represent population-weighted estimates; actual hardness varies by city and water system.