Enter the total calcium content (mg/L) and the total magnesium content (mg/L) into the Calculator. The calculator will evaluate the Water Hardness. 

Water Hardness Formula

The following two example problems outline the steps and information needed to calculate the Water Hardness.

WH = 2.497*Ca + 4.118*Mg


  • WH is the Water Hardness (mg/L)
  • Ca is the total calcium content (mg/L) 
  • Mg is the total magnesium content (mg/L) 

To calculate Water Hardness, multiply the calcium content by 2.497 and add the result to the product of 4.118 times the magnesium content.

How to Calculate Water Hardness?

The following steps outline how to calculate the Water Hardness.

  1. First, determine the total calcium content (mg/L). 
  2. Next, determine the total magnesium content (mg/L). 
  3. Next, gather the formula from above = WH = 2.497*Ca + 4.118*Mg.
  4. Finally, calculate the Water Hardness.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

total calcium content (mg/L) = 3

total magnesium content (mg/L) = 4.25

WH = 2.497*Ca + 4.118*Mg = ?