Calculate total water hardness based on calcium and magnesium concentrations.
Ion Concentrations
mg/L
mg/L
Water Hardness Results
Total Hardness91.12mg/L CaCO₃
Hardness ClassificationModerately Hard
SoftVery Hard
Equivalent Units
Grains/Gallon (gpg)
5.33
mmol/L
0.91
About this calculator
Overview
Water hardness is primarily caused by dissolved calcium and magnesium ions. It is expressed as mg/L of calcium carbonate (CaCO₃) equivalent because different ions contribute differently to technical hardness.
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Pro Tips
Water above 180 mg/L is considered 'Very Hard' and usually requires treatment.
Grains per Gallon (gpg) is another common unit: 1 gpg ≈ 17.1 mg/L.
Use a water softener if you notice scaling in kettles or white spots on glassware.
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Fun Facts
"Hard water can significantly reduce the lifespan of water heaters due to scale buildup."
"Soap reacts with hard water to form 'soap scum' (calcium stearate)."
"Drinking hard water can actually be a good source of dietary calcium and magnesium."
