Created By : Rina Nayak

Reviewed By : Rajashekhar Valipishetty

Last Updated : May 16, 2023

Use our free Water Hardness Calculator tool to estimate the amount of dissolved minerals available in the tap water supply. Minerals such as calcium, and magnesium are present in the regular water. All you have to do is provide calcium content, and magnesium content details and hit the calculate button to get the water hardness value.

Calcium content
Magnesium content
Water Hardness

What is Water Hardness?

Water hardness is the amount of magnesium and calcium dissolved in the water. Depending on the hardness of the water, it is classified as hard, or soft. The water hardness is measured in mg/L, ppm, and mmol/L. In general, hard water is found in areas where limestone, chalk, and gypsum are present in the ground.

The water hardness formula is along the lines:

Water Hardness = Ca * 2.497 + Mg * 4.118


Ca is the amount of calcium

Mg is the amount of magnesium

Hardness of water ranges are tabulated here:

Hardness (mg/CaCO3L) Classification
Moderately hard
very Hard

Steps to Calculate the Water Hardness

  • Make a note of the calcium, magnesium concentrations in mg/L.
  • Multiply calcium concentration with 2.497.
  • Multiply the magnesium concentration with 4.118.
  • Add those 2 products to obtain the water hardness.


Find the water hardness of the supply having calcium concentration as 31 mg/L and magnesium concentration as 27 mg/L.


Given that,

Calcium concentration = 31 mg/L

Magnesium concentration = 27 mg/L

Water hardness formula is

Water Hardness = Ca * 2.497 + Mg * 4.118

= 31 * 2.497 + 27 * 4.118

= 188.6

The water hardness value is 188.6 mg/CaCo3L. So, the water isvery hard.

Frequently Asked Question's on Water Hardness Calculator

1. What is the normal level of hardness in water?

The hardness of water is divided into 4 types: below 60 mg/L as soft, between 61 to 120 mg/L as moderately hard, between 121 to 180 mg/L as hard, and more than 180 mg/L as very hard.

2. What are the units of water hardness?

The units to measure the hardness of water are mg/L, and ppm.

3. What increases water hardness?

Water hardness can be increased in culture water by adding multiple compounds like calcium sulfate, and calcium chloride.

4. What is the pH of hard water?

The pH level of hard water is above 8.5.