Their are two types of water hardness. Temporary and permanent hardness. This calculator determines the permanent total hardness. For information about the temporary water hardness

Total permanent water hardness is calculated with the following formula:

TOTAL PERMANENT HARDNESS = CALCIUM HARDNESS + MAGNESIUM HARDNESS

The calcium and magnesium hardness is the concentration of calcium and magnesium ions expressed as equivalent of calcium carbonate. The molar mass of CaCO₃, Ca²⁺ and Mg²⁺ are respectively 100,1 g/mol, 40,1 g/mol and 24,3 g/mol.
The ratio of the molar masses are:

So total permanent water hardness expressed as equivalent of CaCO₃ can be calculated with the following formula:

The following calculator computes and gives an indication of the total water hardness. Fields with * are required.

	*	mg/L g/m3 ppm mol/L mmol/L eq/L meq/L
	*	mg/L g/m3 ppm mol/L mmol/L eq/L meq/L
Water Hardness		mg/L or ppm of CaCO3
		French degree
		German degree
		English degree
		Indication

The following values are used to give an indication about the water hardness: