Water Hardness by City and Country

Hardness is expressed as mg/L of calcium carbonate (CaCO₃) equivalent. The four standard bands, used by the USGS and on every city page on this site:

To convert: multiply mg/L by 0.056 for German degrees, by 0.10 for French degrees, or by 0.058 for grains per gallon. For a deeper explanation of what these numbers mean and where hardness comes from geologically, see our water hardness explainer.

Three practical ways to find out how hard your water is:

• Your utility's water quality report (CCR). In the US, every public water system publishes an annual Consumer Confidence Report with hardness data. In the EU, utilities report hardness on request or online. This is the most accurate source — it comes from lab testing of your actual supply.
• Home test strips or liquid drop kits. Hardness test strips cost a few dollars for a pack and give a ballpark reading in seconds. Liquid titration kits (count the drops until the water changes color) are more precise. Either is good enough to place your water in the right band above.
• TDS meters — with caveats. A TDS meter measures total dissolved solids, not hardness specifically. Hardness is a subset of TDS, so a high TDS reading suggests hard water, but the meter cannot distinguish calcium from sodium or chloride. It is not a substitute for a hardness test. See our TDS guide for what these meters actually measure.

Every city page on this site includes the local hardness level. Check your city's page directly, or browse the country-by-country overview to see how your region compares.

Hardness is not a health concern, but it shows up in everyday ways:

• Taste. Moderately hard water (60–120 mg/L) generally tastes pleasant and rounded. Very soft water can taste flat; very hard water can taste chalky or mineral-heavy.
• Limescale. Hard water leaves white calcium carbonate deposits inside kettles, on shower heads, in dishwashers, and on heating elements. Scale builds faster at higher temperatures and higher hardness, shortening appliance life and reducing energy efficiency.
• Soap and detergent. Calcium reacts with soap to form insoluble scum, meaning poor lather, filmy residue on skin and hair, spots on glassware, and stiffer laundry. You typically need more detergent in hard water areas — check the packaging for separate dosing recommendations.
• Hair and skin. The soap-scum residue from hard water can leave hair feeling dry or coated and skin feeling tight after washing. This is a cosmetic effect, not a medical one, and is managed by choosing syndet (synthetic detergent) cleansers or using a chelating shampoo.
• Coffee and tea. Brewing with very hard water can produce a flat, chalky cup. Specialty coffee associations recommend 50–150 mg/L for optimal extraction. If your water is much harder, a filtered brew or blending with softer bottled water improves results.

The WHO sets no health-based guideline for water hardness and finds no evidence that hard water causes harm at any level found in drinking supplies. Calcium and magnesium are essential nutrients, and hard water contributes a modest share of daily intake — some epidemiological research has even associated harder water with slightly lower cardiovascular risk, though the evidence is not strong enough to be conclusive.

Kidney stones: the claim that hard water causes kidney stones is not supported by the evidence for typical drinking-water hardness levels. Kidney stone formation is influenced by genetics, diet, hydration, and metabolic factors — not by whether your tap water is at 100 or 200 mg/L. Staying well hydrated with any water is the most effective preventive measure.

For the full scientific breakdown, including the relationship between hardness and TDS, see our detailed hardness guide.

If hardness is causing limescale or soap problems, here are the options that actually work — and some that don't:

• Ion-exchange water softeners replace calcium and magnesium with sodium. They are the standard whole-house solution and effectively eliminate scale. The trade-off: softened water contains added sodium, so most installers leave the kitchen cold tap unsoftened for drinking and cooking.
• Reverse osmosis (RO) removes hardness along with virtually all dissolved solids. It is effective but produces wastewater and is typically installed as a point-of-use system under the kitchen sink rather than whole-house.
• Citric acid and vinegar descaling dissolves existing limescale from kettles, coffee makers, and shower heads. Run a citric acid cycle monthly in areas with hard water. It does not prevent new buildup, but it is cheap and effective maintenance.
• Dishwasher salt regenerates the built-in softener in European-style dishwashers. If you live in a hard water area and your glassware is spotty, check that the salt reservoir is full and the hardness dial is set correctly.

What does not work:

• Magnetic and electronic “water conditioners” claim to alter calcium crystals so they don't form scale. Independent testing has consistently failed to confirm any meaningful effect. Save your money.
• Filter pitchers (e.g., Brita) use activated carbon to improve taste and remove chlorine, but they do not significantly reduce hardness. If hardness is your problem, a carbon pitcher is not the answer.

Check your city's hardness on its dedicated page to see whether treatment is worth considering, or browse the country overview to compare levels across regions.