WaterProfile Local

Utilities / Wisconsin

Madison, WI water hardness

Madison Water Utility publishes a hardness range of 18 to 20 grains per gallon for its system, on the page cited below. At 17.1 mg/L per grain that is 307.8 to 342 mg/L. On the USGS scale that is very hard water.

Soft Moderate Hard Very hard 0 60 120 180 500+ 324.9 mg/L Madison, WI sits in the very hard band mg/L as CaCO₃. Bands drawn equal width, so the axis is not linear.
Madison Water Utility published 18 to 20 grains per gallon, shown here as the bar converted to 307.8 to 342 mg/L at 17.1 mg/L per grain. The plotted point is the midpoint of the published gpg range, converted at 17.1 mg/L per gpg. Classification bands from the USGS Water Science School.

The published figure, exactly as it appears

This is the hardness line transcribed from the source, with nothing added:

This water contains 18-20 grains of hardness per gallon.

Madison Water Utility

Units as published: grains of hardness per gallon. What kind of figure it is: a range with no average. Retrieved 2026-10-17.

Madison hardness in mg/L and grains per gallon

Water-quality reports use mg/L (identical to ppm). Softener instructions and plumbing specifications use grains per gallon. Both are below. Where a figure is our arithmetic rather than the utility's own number, it says so.

Figuremg/L (ppm)Grains per gallonWhose number
Low end of published range307.818gpg published, mg/L is our conversion
High end of published range34220gpg published, mg/L is our conversion
Plotted on the scale above324.919midpoint of the published gpg range, converted at 17.1 mg/L per gpg; the gpg here is our conversion at 17.1, so it can differ slightly from a utility’s own rounded gpg figure

The conversion, both ways: gpg = mg/L ÷ 17.1 and mg/L = gpg × 17.1. Worked for this system: 324.9 ÷ 17.1 = 19 gpg. The converter does °dH and °f as well, and why the factor is 17.1 explains where the number comes from.

What this figure does not tell you

Service area and source water

UtilityMadison Water Utility
Service area as publishedMadison Water Utility's system. The utility draws from a number of separate wells and publishes a water quality report for each one; this range is its own summary figure for its water generally.

Provenance of every number on this page

Source documentMadison Water Utility water quality frequently asked questions
Source URLhttps://www.cityofmadison.com/water/water-quality/faq
Published byMadison Water Utility
Report yearNot stated on the source page
Year noteThe FAQ answer states no year for the hardness range and cites no report.
Retrieved2026-10-17
Classification bandsUSGS Water Science School, retrieved 2026-10-16

Notes the report forces on this page

If you are sizing a softener for Madison water

At 19 gpg, the sizing arithmetic starts from your household's water use, not from the hardness alone. The calculator below is pre-filled with this system's figure and every other input is an editable assumption.

Whether a softener is worth installing at this hardness is a judgement, not arithmetic, and it is not one this site makes for you. Nothing here has been tested by the author.

Where Madison sits against other verified systems

Soft Soft 0–60
Moderately hard Moderate 61–120
Hard Hard 121–180
Very hard Very hard 181+
  1. Portland, OR 9 mg/L 0.5 gpg Soft
  2. Boston, MA 16 mg/L 1 gpg Soft
  3. Manchester, NH 17.9 mg/L 1 gpg Soft
  4. Raleigh, NC 25 mg/L 1.47 gpg Soft
  5. New York, NY 32 mg/L 2 gpg Soft
  6. Charlotte, NC 32 mg/L 1.9 gpg Soft
  7. Memphis, TN 46 mg/L 2.7 gpg Soft
  8. Anchorage, AK 56 mg/L 3.3 gpg Soft
  9. Oakland, CA 68.4 mg/L 4 gpg Moderately hard
  10. Nashville, TN 77.3 mg/L 4.5 gpg Moderately hard
  11. Sacramento, CA 83 mg/L 4.9 gpg Moderately hard
  12. Fresno, CA 89.3 mg/L 5.2 gpg Moderately hard
  13. Saint Paul, MN 90 mg/L 5 gpg Moderately hard
  14. Austin, TX 93 mg/L 5.4 gpg Moderately hard
  15. Washington, DC 95 mg/L 5.6 gpg Moderately hard
  16. Birmingham, AL 98 mg/L 5.7 gpg Moderately hard
  17. Kansas City, MO 100 mg/L 5.8 gpg Moderately hard
  18. Denver, CO 105 mg/L 6.1 gpg Moderately hard
  19. Tulsa, OK 114.5 mg/L 6.7 gpg Moderately hard
  20. Louisville, KY 115 mg/L 6.7 gpg Moderately hard
  21. Columbus, OH 120 mg/L 7 gpg Moderately hard
  22. Cleveland, OH 120 mg/L 7 gpg Moderately hard
  23. Philadelphia, PA 125 mg/L 7.3 gpg Hard
  24. Ann Arbor, MI 126 mg/L 7.4 gpg Hard
  25. Cincinnati, OH 133 mg/L 7.8 gpg Hard
  26. Milwaukee, WI 137 mg/L 8.01 gpg Hard
  27. St. Louis, MO 138 mg/L 8.1 gpg Hard
  28. Fort Worth, TX 145 mg/L 8.5 gpg Hard
  29. Honolulu, HI 162.5 mg/L 9.5 gpg Hard
  30. Wichita, KS 170 mg/L 9.9 gpg Hard
  31. Omaha, NE 170 mg/L 10 gpg Hard
  32. Los Angeles, CA 192 mg/L 11.2 gpg Very hard
  33. Lincoln, NE 192 mg/L 11.2 gpg Very hard
  34. Tampa, FL 220 mg/L 12.9 gpg Very hard
  35. Phoenix, AZ 237 mg/L 13.9 gpg Very hard
  36. Mesa, AZ 239.4 mg/L 14 gpg Very hard
  37. San Diego, CA 276 mg/L 16 gpg Very hard
  38. Las Vegas, NV 280 mg/L 16 gpg Very hard
  39. Chandler, AZ 282.2 mg/L 16.5 gpg Very hard
  40. San Antonio, TX 299.3 mg/L 17.5 gpg Very hard
  41. Anaheim, CA 300 mg/L 18 gpg Very hard
  42. Indianapolis, IN 317 mg/L 19 gpg Very hard
  43. Madison, WI 324.9 mg/L 19 gpg Very hard
  44. Scottsdale, AZ 352.5 mg/L 20.6 gpg Very hard

mg/L as calcium carbonate. Each classification band is drawn the same width, so the axis is not linear in mg/L.

Madison, WI is the highlighted row. Every other system on this chart has its own page with its own published figure and report date. Grains per gallon are the utility's own figure where it published one, and our conversion at 17.1 mg/L per grain where it did not.

Systems with similar published hardness

All 44 verified systems   How to find hardness in your own utility's report   If you are on a well instead