Guides

How to get a hardness figure you can trust, and what it does and does not mean once you have it.

• How to read a water quality report

  Where hardness hides in a Consumer Confidence Report, what MCL and SMCL mean, why the column heading matters more than the number, and how to tell when the figure genuinely is not published.

• Municipal water hardness vs well water

  Why a utility figure cannot be borrowed for a private well, what is actually the same between the two, and how to get a number you can size equipment from.

• Unit guides, October 16, 2026

  Water Hardness ppm to gpg: The Conversion, Explained

  Water hardness ppm to gpg: divide ppm by 17.1. Here is the conversion table, where the 17.1 comes from, and the mistakes that produce wrong answers.

Tools

• Water hardness converterppm, mg/L, gpg, °dH, °f and ppb, with every formula printed.
• Water softener grain capacity calculatorHardness, household size and regeneration interval to grains, with each assumption labelled and editable.

Verified utility figures   Methodology and sources