Check Your Water Hardness
Free water hardness data for every zip code in the US. Powered by EPA and USGS data covering 31,389 zip codes and 48,068 water systems.
What Is Water Hardness?
Water hardness measures the dissolved mineral content in your water, primarily calcium and magnesium. It's measured in parts per million (PPM) or grains per gallon (GPG). Hard water is a common issue across much of the United States, affecting everything from your plumbing and appliances to your skin and hair.
Use our water hardness scale to compare PPM and GPG levels, or see the hard water vs soft water guide for a side-by-side comparison.
Scale Buildup
Hard water leaves mineral deposits in pipes, water heaters, and fixtures, reducing efficiency and lifespan.
Skin & Hair
Minerals in hard water can leave skin feeling dry and hair looking dull. A water softener or shower filter can help.
Appliance Damage
Dishwashers, washing machines, and water heaters work harder and wear out faster with hard water.
Understand Your Water
Water Hardness Scale: PPM and GPG Chart
Use the USGS water hardness scale to compare PPM, GPG, and mg/L levels from soft to very hard water.
10 min readHard Water vs Soft Water: Key Differences
Compare hard water and soft water by minerals, taste, soap lather, skin, hair, plumbing, and treatment needs.
10 min readHow to Test Water Hardness at Home
Compare free lookups, soap tests, test strips, liquid drop kits, and lab tests for measuring water hardness.
8 min readDo You Need a Water Softener? (Based on Your Water Hardness)
A data-driven guide to help you decide if a water softener is worth the investment based on your actual water hardness level.
10 min read