Water Hardness Calculator

The Water Hardness Calculator estimates dissolved mineral content from calcium and magnesium concentrations in tap water. Hardness is reported as mg/L equivalent to calcium carbonate (CaCO₃) and helps classify water as soft, moderately hard, hard, or very hard.

Water hardness formula

When calcium and magnesium are given in mg/L, total hardness as CaCO₃ is:

$$\mathrm{Hardness} = 2.497 \times \mathrm{Ca} + 4.118 \times \mathrm{Mg}$$

The result is in mg/L as CaCO₃, which is equivalent to ppm for water at standard conditions.

Hardness classification

0-60 mg/L: Soft
61-120 mg/L: Moderately hard
121-180 mg/L: Hard
181-240 mg/L: Very hard
Above 240 mg/L: Extremely hard

Frequently Asked Questions

What is water hardness?

Water hardness measures dissolved calcium and magnesium ions, usually reported as mg/L equivalent to CaCO₃. It affects scaling in pipes, soap efficiency, and appliance performance.

How do I calculate water hardness from Ca and Mg?

Multiply calcium in mg/L by 2.497, multiply magnesium in mg/L by 4.118, then add the two values. The sum is hardness in mg/L as CaCO₃.

Is mg/L the same as ppm for hardness?

Yes. For water at standard density, mg/L and ppm are equivalent for dissolved solids and hardness values.

What hardness level is considered soft water?

Water with hardness below 60 mg/L as CaCO₃ is classified as soft. Values above 180 mg/L are very hard and may cause noticeable scaling.

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Water Hardness Calculator