Water Hardness Calculator

Water hardness measures the concentration of dissolved minerals — mainly calcium and magnesium — in your water supply, and high levels can cause scale buildup in pipes, appliances, and kettles. Enter your Calcium (Ca²⁺) and Magnesium (Mg²⁺) concentrations, select their units, and choose your preferred output unit to get the Total Water Hardness. Secondary outputs include hardness in grains per gallon, a water classification (e.g. soft, hard, very hard), and the individual hardness contributions from calcium and magnesium. Also try the find Molar Mass with Molar Mass of Gas Calculator.

Results

Total Water Hardness

Hardness (Grains per Gallon)

Water Classification

Calcium Hardness Contribution

Magnesium Hardness Contribution

Results Table

What is water hardness and why does it matter?

Water hardness refers to the concentration of dissolved calcium and magnesium ions in water. Hard water can cause scale buildup in pipes and appliances, reduce soap effectiveness, and affect the taste of water. See also our use the PPM to Molarity Calculator.

How do I measure calcium and magnesium levels in my water?

You can use water test strips, digital TDS meters, or have your water professionally tested. Many municipal water suppliers also provide water quality reports that include hardness levels.

What's the difference between ppm, gpg, and degrees of hardness?

PPM (mg/L as CaCO₃) is the most common unit, gpg (grains per gallon) is popular in the US, while °dH (German degrees) and °fH (French degrees) are used in Europe. All measure the same thing in different scales.

What levels are considered soft, moderate, hard, or very hard water?

Soft water: 0-60 ppm, Moderately hard: 61-120 ppm, Hard: 121-180 ppm, Very hard: >180 ppm. These classifications help determine if water treatment is needed. You might also find our Solution Dilution Calculator useful.

What are the common signs of hard water at home?

White scale deposits on faucets and showerheads, soap scum buildup, reduced lather from soap, dry skin and hair, and spotted dishes after washing are typical signs of hard water.

How does hard water affect plumbing and appliances?

Hard water causes mineral buildup in pipes, reducing water flow over time. It can also shorten the lifespan of water heaters, dishwashers, and washing machines by causing scale accumulation.

What is the best treatment for hard water?

Water softeners that use ion exchange are the most effective for removing calcium and magnesium. Salt-free conditioners can help with scale control, while reverse osmosis systems provide comprehensive water purification.

How accurate is this calculator compared to professional testing?

This calculator provides accurate results when you input correct calcium and magnesium concentrations. For the most precise measurements, professional water testing is recommended, especially for critical applications.