Water Hardness by ZIP Code

1. Check your water hardness

How ZIP lookup works: the hardness dataset is published by city, not by ZIP. We take your ZIP code's Census centroid and show the value reported for the nearest city in the dataset - check the distance shown on the result. On a private well? City data does not apply to well water; test it with a hardness test kit instead.

2. Water softener sizing calculator

Industry-standard sizing: grains per day = people x gallons per person per day x hardness (gpg). Weekly capacity need = daily grains x 7 days x 1.3 safety factor, rounded up to the next standard softener size (24,000 / 32,000 / 40,000 / 48,000 / 64,000 grains).

USGS water hardness classification

Classification per the USGS Water Science School. Conversion: gpg = mg/L ÷ 17.1.

Water hardness in the 30 largest US cities

All 30 values are utility-reported (tier T1) in the source dataset - see Data & sources below.

Browse water hardness by state

• Alabama - 385 cities, median 63 mg/L
• Alaska - 47 cities, median 62 mg/L
• Arizona - 153 cities, median 180 mg/L
• Arkansas - 388 cities, median 48 mg/L
• California - 1015 cities, median 108 mg/L
• Colorado - 272 cities, median 113 mg/L
• Connecticut - 111 cities, median 53 mg/L
• Delaware - 57 cities, median 50 mg/L
• District of Columbia - 2 cities, median 120 mg/L
• Florida - 465 cities, median 103 mg/L
• Georgia - 382 cities, median 25 mg/L
• Hawaii - 44 cities, median 67 mg/L
• Idaho - 100 cities, median 124 mg/L
• Illinois - 674 cities, median 249 mg/L
• Indiana - 404 cities, median 268 mg/L
• Iowa - 393 cities, median 314 mg/L
• Kansas - 344 cities, median 250 mg/L
• Kentucky - 283 cities, median 122 mg/L
• Louisiana - 278 cities, median 48 mg/L
• Maine - 124 cities, median 35 mg/L
• Maryland - 207 cities, median 117 mg/L
• Massachusetts - 340 cities, median 45 mg/L
• Michigan - 475 cities, median 216 mg/L
• Minnesota - 390 cities, median 240 mg/L
• Mississippi - 268 cities, median 24 mg/L
• Missouri - 673 cities, median 195 mg/L
• Montana - 92 cities, median 169 mg/L
• Nebraska - 196 cities, median 283 mg/L
• Nevada - 57 cities, median 124 mg/L
• New Hampshire - 90 cities, median 18 mg/L
• New Jersey - 544 cities, median 82 mg/L
• New Mexico - 148 cities, median 186 mg/L
• New York - 683 cities, median 85 mg/L
• North Carolina - 544 cities, median 28 mg/L
• North Dakota - 102 cities, median 390 mg/L
• Ohio - 561 cities, median 253 mg/L
• Oklahoma - 368 cities, median 183 mg/L
• Oregon - 225 cities, median 38 mg/L
• Pennsylvania - 1079 cities, median 92 mg/L
• Rhode Island - 44 cities, median 23 mg/L
• South Carolina - 230 cities, median 22 mg/L
• South Dakota - 97 cities, median 460 mg/L
• Tennessee - 312 cities, median 81 mg/L
• Texas - 1266 cities, median 107 mg/L
• Utah - 174 cities, median 256 mg/L
• Vermont - 79 cities, median 56 mg/L
• Virginia - 307 cities, median 78 mg/L
• Washington - 386 cities, median 43 mg/L
• West Virginia - 193 cities, median 97 mg/L
• Wisconsin - 442 cities, median 208 mg/L
• Wyoming - 68 cities, median 198 mg/L

How softener sizing works

Multiply the people in your home by the water each person uses per day (75 gallons is the standard planning figure) and by your water hardness in grains per gallon. That is the grains of hardness a softener must remove each day. Sizing for seven days between regenerations, plus a 30% reserve (the x1.3 factor), keeps the resin bed from exhausting before regeneration day. Example: 4 people x 75 gallons x 10 gpg = 3,000 grains per day; x 7 x 1.3 = 27,300 grains per week, so a 32,000-grain softener is the right size.

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