Water Hardness Calculator
Calculate water hardness from calcium and magnesium concentrations with classification
Calculate Water Hardness
Concentration of calcium ions in water
Concentration of magnesium ions in water
Formula Explanation
Water Hardness: Hardness = 2.497 × [Ca²⁺] + 4.118 × [Mg²⁺]
Conversion factors: Based on equivalent weights of CaCO₃
Units: Result expressed as mg/L CaCO₃ (calcium carbonate equivalent)
Note: All concentrations converted to mg/L before calculation
Example Calculation
Well Water Analysis
Sample: Municipal water supply analysis
Calcium concentration: 31 mg/L
Magnesium concentration: 27 mg/L
Step-by-Step Solution
1. Apply formula: Hardness = 2.497 × Ca²⁺ + 4.118 × Mg²⁺
2. Substitute values: Hardness = 2.497 × 31 + 4.118 × 27
3. Calculate: Hardness = 77.4 + 111.2 = 188.6 mg/L CaCO₃
4. Classification: 188.6 mg/L falls in "Very Hard" category (181-240 mg/L)
Result: 188.6 mg/L CaCO₃ - Very Hard Water
Common Water Types
Distilled Water
Ca²⁺: 0 mg/L, Mg²⁺: 0 mg/L
Hardness: 0 mg/L CaCO₃
Rainwater
Ca²⁺: 2 mg/L, Mg²⁺: 1 mg/L
Hardness: 9 mg/L CaCO₃
Soft Well Water
Ca²⁺: 20 mg/L, Mg²⁺: 8 mg/L
Hardness: 83 mg/L CaCO₃
Moderate Tap Water
Ca²⁺: 40 mg/L, Mg²⁺: 15 mg/L
Hardness: 162 mg/L CaCO₃
Hard Well Water
Ca²⁺: 60 mg/L, Mg²⁺: 25 mg/L
Hardness: 253 mg/L CaCO₃
Very Hard Water
Ca²⁺: 80 mg/L, Mg²⁺: 35 mg/L
Hardness: 344 mg/L CaCO₃
Hardness Classification
Water Hardness Tips
Ca²⁺ and Mg²⁺ are primary hardness ions
Hardness expressed as CaCO₃ equivalent
Hard water causes soap scum and scaling
Soft water may taste flat or salty
Water softeners remove hardness ions
Understanding Water Hardness
What is Water Hardness?
Water hardness is a measure of dissolved minerals, primarily calcium (Ca²⁺) and magnesium (Mg²⁺) ions, in water. Hard water is common in areas with limestone, gypsum, and chalk deposits in the ground.
Effects of Hard Water
- •Soap scum formation and reduced lather
- •Mineral deposits and scaling in pipes
- •Reduced efficiency of water heaters
- •Spots on dishes and glassware
- •Dry skin and hair after bathing
Types of Hardness
Temporary Hardness
Caused by bicarbonates (Ca(HCO₃)₂, Mg(HCO₃)₂). Can be removed by boiling.
Permanent Hardness
Caused by sulfates and chlorides (CaSO₄, MgSO₄, CaCl₂, MgCl₂). Cannot be removed by boiling.
Treatment Methods
- Ion Exchange: Replace Ca²⁺ and Mg²⁺ with Na⁺
- Lime Softening: Precipitate hardness minerals
- Reverse Osmosis: Remove dissolved minerals
- Chelation: Bind hardness ions chemically
Unit Conversion Reference
Hardness Unit Conversions
| From | To mg/L CaCO₃ |
|---|---|
| 1 gpg | 17.12 mg/L CaCO₃ |
| 1 °dH | 17.8 mg/L CaCO₃ |
| 1 °fH | 10.0 mg/L CaCO₃ |
| 1 °eH | 14.3 mg/L CaCO₃ |
Ion Conversion Factors
Calcium (Ca²⁺)
Factor: 2.497
Based on CaCO₃/Ca atomic weight ratio
Magnesium (Mg²⁺)
Factor: 4.118
Based on CaCO₃/Mg atomic weight ratio
Note: Factors account for charge balance and molecular weight differences.