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Water Hardness Calculator
Calculate total water hardness from calcium and magnesium levels.
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About Water Hardness
Water hardness is primarily caused by dissolved calcium and magnesium. It is commonly expressed as milligrams of calcium carbonate equivalent per liter.
Classification Scale
- Soft: 0 - 60 mg/L
- Moderately Hard: 61 - 120 mg/L
- Hard: 121 - 180 mg/L
- Very Hard: > 180 mg/L
Understanding Water Hardness
Water hardness is caused by dissolved calcium (Ca²⁺) and magnesium (Mg²⁺) ions. These minerals enter groundwater as it percolates through limestone and chalk deposits. While not harmful to health, hard water causes practical problems in homes and industries.
Water Hardness Classification Scale
| Classification | mg/L (CaCO₃) | gpg |
|---|---|---|
| Soft | 0-60 | 0-3.5 |
| Moderately Hard | 61-120 | 3.5-7 |
| Hard | 121-180 | 7-10.5 |
| Very Hard | >180 | >10.5 |
💡 Expert Tip: Get a Free Water Report
Before buying an expensive water softener, request a free water quality report from your municipal water supplier. In the US, utilities are required to provide an annual Consumer Confidence Report (CCR) that includes hardness data. This can save you from unnecessary equipment purchases!
⚠️ Common Mistake: "Hard Water is Unhealthy"
Hard water is NOT bad for your health. Calcium and magnesium are essential minerals, and the WHO states that drinking hard water can contribute to your daily intake. The problems are cosmetic (dry skin, spotty dishes) and mechanical (appliance damage), not health-related.
Effects of Hard Water
- Scale Buildup: Limescale clogs pipes and reduces water heater efficiency (increases energy costs by 15-25%)
- Reduced Soap Effectiveness: Requires 2-3x more detergent for cleaning
- Appliance Damage: Shortens lifespan of dishwashers, washing machines, and coffee makers
- Skin & Hair: Can cause dryness and dullness
Reviewed by: Dr. Lisa Martinez, Water Quality
Specialist
Last updated: November 27, 2025
Frequently Asked Questions
What is water hardness and why does it matter?
Water hardness is dissolved calcium and magnesium. It causes scale buildup and reduces soap effectiveness, but is not harmful to health.
Is hard water bad for your health?
No. Calcium and magnesium are beneficial minerals. The WHO states hard water can contribute to daily mineral intake.
How do I test my water hardness at home?
Use test strips ($10-20) from hardware stores or request a free report from your water utility.
Do I need a water softener?
If hardness exceeds 120 mg/L (7 gpg) and you experience limescale buildup or frequent appliance repairs, yes.