This water hardness calculator is created to compute the precise level of calcium (Ca²⁺) and magnesium (Mg²⁺) ions, in water using Water Hardness (mg/L as CaCO₃) = (2.5 × [Ca²⁺]) + (4.1 × [Mg²⁺]) formula.
Water hardness is typically expressed in various units, including:
- Grains per gallon (gpg)
- Parts per million (ppm)
- Milligrams per liter (mg/L)
- Millimoles per liter (mmol/L)
Water Hardness Calculator
| Ca²⁺ (mg/L) | Mg²⁺ (mg/L) | Total Hardness (ppm as CaCO₃) | Classification |
|---|---|---|---|
| 30 | 10 | 116.3 | Moderately Hard |
| 50 | 15 | 186.5 | Hard |
| 70 | 20 | 257.2 | Very Hard |
| 20 | 5 | 70.4 | Soft |
| 40 | 12 | 149.3 | Moderately Hard |
| 25 | 8 | 97.0 | Moderately Hard |
| 60 | 25 | 245.4 | Very Hard |
| 15 | 3 | 52.1 | Soft |
| 80 | 30 | 319.0 | Very Hard |
| 45 | 10 | 175.0 | Hard |
| 10 | 2 | 35.7 | Soft |
| 55 | 18 | 223.4 | Very Hard |
| 35 | 5 | 130.5 | Moderately Hard |
| 90 | 40 | 382.4 | Extremely Hard |
| 5 | 1 | 17.9 | Soft |
Water Hardness Calculation Formula
The formula for calculating water hardness is:
Total Hardness (as CaCO₃) = [2.497 × Ca²⁺ (mg/L)] + [4.118 × Mg²⁺ (mg/L)]Where
- Calcium (Ca²⁺) = 40 mg/L
- Magnesium (Mg²⁺) = 12 mg/L
Calculation:
Total Hardness = (2.497 × 40) + (4.118 × 12)
= 99.88 + 49.416
= 149.296 mg/L as CaCO₃Water Hardness Classifications:
- Soft: 0-60 ppm
- Moderately Hard: 61-120 ppm
- Hard: 121-180 ppm
- Very Hard: >180 ppm
How to Calculate the Hardness of Water?
- Step 1: Calculate calcium hardness as CaCO₃: Ca²⁺ as CaCO₃ = 40 mg/L × 2.497 = 99.88 mg/L
- Step 2: Calculate magnesium hardness as CaCO₃: Mg²⁺ as CaCO₃ = 15 mg/L × 4.116 = 61.74 mg/L
- Step 3: Calculate total hardness: Total Hardness = 99.88 + 61.74 = 161.62 mg/L (ppm)
- Step 4: Convert to grains per gallon (optional): Grains per gallon = 161.62 ÷ 17.1 = 9.45 gpg
The water sample has a hardness of 161.62 ppm (9.45 gpg), classifying it as “Hard” water.
Total Hardness Calculation by EDTA Method
The EDTA (Ethylenediaminetetraacetic acid) titration method is a widely used laboratory technique for measuring total water hardness. This method involves:
- Sample Preparation
- Take 50mL water sample
- Add ammonia buffer solution
- Add Eriochrome Black T indicator
- Titration Process
- Titrate with standardized EDTA solution
- Note volume at end point (color change from wine red to blue)
Calculation: Total Hardness (mg/L as CaCO₃) = (V × N × 1000 × 100) / S Where: V = Volume of EDTA used (mL) N = Normality of EDTA S = Sample volume (mL)How to Calculate Total Hardness of Water in PPM
Here’s the process:
- Basic Conversion
- 1 grain per gallon (gpg) = 17.1 ppm
- 1 mg/L = 1 ppm
- Calculation Example: If your water has 8 gpg hardness:
Hardness in ppm = 8 gpg × 17.1 = 136.8 ppm
References
- World Health Organization (WHO) – Guidelines for Drinking-water Quality https://www.who.int/water_sanitation_health/water-quality/guidelines/en/
- United States Geological Survey (USGS) – Water Hardness https://www.usgs.gov/special-topics/water-science-school/science/hardness-water
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