Water Hardness Unit Conversion
Water hardness is a key indicator of divalent metal ions like calcium and magnesium in water. Different units are used across industrial water treatment, boiler feedwater, pure water production, and municipal supply systems. This table uses CaCO₃ (calcium carbonate) as the standard conversion reference.
I. Unit Conversion Table
| Unit | mg/L (as CaCO₃) | mmol/L | °dH (German degrees of hardness) | °FH (French degrees) | °eH (British degrees) |
|---|---|---|---|---|---|
| 1 mg/L (CaCO₃) | 1 | 0.0200 | 0.0560 | 0.1000 | 0.0700 |
| 1 mmol/L | 50.04 | 1 | 2.804 | 5.004 | 3.503 |
| 1 °dH (German degrees) | 17.848 | 0.3567 | 1 | 1.7848 | 1.249 |
| 1 °fH (French Hardness) | 10 | 0.1998 | 0.5603 | 1 | 0.7002 |
| 1 °eH (UK degrees) | 14.286 | 0.2855 | 0.8004 | 1.4286 | 1 |
II. Water Hardness Grade Reference
| Water Quality Classification | mg/L (as CaCO₃) | °dH (German degrees of hardness) |
|---|---|---|
| Ultra-soft water | 0～50 | 0～2.8 |
| Soft water | 50～100 | 2.8～5.6 |
| Medium | 100～200 | 5.6～11.2 |
| Hard water | 200～300 | 11.2～16.8 |
| Very Hard Water | ＞300 | ＞16.8 |
3. Ion-Hardness Conversion
| Ion | Conversion formula |
|---|---|
| Calcium ion | Ca²⁺ (mg/L) × 2.505 = Calcium Hardness (mg/L as CaCO₃) |
| Magnesium ion | Mg²⁺ (mg/L) × 4.118 = Magnesium Hardness (mg/L as CaCO₃) |
Total Hardness = Calcium Hardness + Magnesium Hardness
IV. Instructions
1. Unless otherwise specified, water quality ppm in the industry is equivalent to mg/L (as CaCO₃).
2. The Lomet Online Hardness Analyzer defaults to mg/L (as CaCO₃) and supports switching the display unit to German degrees °dH or mmol/L via the interface.
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