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Free conversion and setup tool
Dishwasher Water Hardness Converter
Turn the number from a water report, test strip, or utility into the units used by your dishwasher manual—and understand which settings to check next.
The calculation runs in your browser. Nothing is uploaded or saved, and the tool never invents a model-specific detergent or salt dose.
Where to find your water hardness
- Search your local water utility’s annual water-quality report or hardness page.
- For a private well or household softener, use a recent laboratory result or a hardness test made for water—not a pool-only interpretation chart.
- Read the unit beside the result. A value of “10” means very different things in gpg, °dH, and mg/L.
- If your result lists separate calcium and magnesium instead of total hardness as CaCO₃, do not enter either value alone.
Classification and conversion basis
The U.S. Geological Survey classifies 0–60 mg/L as soft, 61–120 mg/L as moderately hard, 121–180 mg/L as hard, and more than 180 mg/L as very hard, expressed as calcium carbonate. One U.S. grain per gallon is approximately 17.1 mg/L.
This calculator uses: 1 gpg = 17.12 mg/L; 1 °dH = 17.848 mg/L; 1 °fH = 10 mg/L; 1 °Clark = 14.254 mg/L; and 1 mmol/L as CaCO₃ = 100.0869 mg/L. Rounded display values may differ slightly from a manual’s conversion table.
Sources and scope notes
- U.S. Geological Survey: Hardness of Water — hardness definition and U.S. classification ranges.
- U.S. Geological Survey report — grains-per-gallon conversion to mg/L.
- Bosch dishwasher setup guidance — model settings, dishwasher salt, rinse aid, detergent, and hard-water limits.
- Whirlpool rinse-aid guidance — water spots, drying, hard water, and model-specific instructions.
Classification describes mineral hardness; it is not a health or drinking-water safety rating. Always use the exact hardness table and product instructions supplied for your dishwasher.
Related troubleshooting
For visible film, compare the white residue guide and cloudy glasses guide. For wet dishes, use the dishwasher drying guide.
Common questions
Dishwasher Water Hardness Converter FAQ
- Why are water-hardness values reported in different units? Utilities, test strips, softeners, detergent labels, and appliance manuals may use ppm, mg/L as calcium carbonate, grains per gallon, or German, French, and English degrees. Converting the same measured value makes those documents easier to compare.
- Where should I get the number to convert? Use a current local water-quality report, a suitable test result taken at the dishwasher supply, or information from the water-treatment provider. Do not copy a regional average when a softener, private well, building system, or seasonal source can change the actual water.
- Will the hardness band tell me an exact salt or detergent setting? No. It supplies a converted measurement and a general classification. The dishwasher manual and product label determine whether the machine has a softener, which scale its setting uses, and the allowed salt, rinse-aid, and detergent adjustments.