Water Hardness Lookup
Enter your ZIP to get your area's water hardness in grains per gallon, sourced from USGS and water authority data, plus a softener recommendation.
Water hardness scale
| Category | GPG | mg/L (PPM) | What you notice |
|---|---|---|---|
| Soft | 0 – 3 | 0 – 50 | No scale; soaps lather easily |
| Slightly hard | 3.5 – 7 | 60 – 120 | Minor spots on glass; acceptable for most appliances |
| Moderately hard | 7 – 10.5 | 120 – 180 | Visible scale on fixtures; water heater efficiency drops ~15% |
| Hard | 10.5 – 14 | 180 – 240 | Heavy scale; water heater life shortened; softener recommended |
| Very hard | > 14 | > 240 | Rapid appliance damage; softener strongly recommended |
What does water hardness actually cost you?
Hard water (above 7 GPG) deposits calcium carbonate scale inside water heaters, reducing thermal efficiency. A University of New Mexico study found that a standard tank water heater loses roughly 1.5% efficiency per GPG of hardness over its lifespan. At 18 GPG (Kansas, Nebraska, Arizona), that's 27% efficiency loss — equivalent to paying for 1.27 water heaters' worth of energy.
How is your water hardness determined?
- ZIP to state. Your ZIP's first 3 digits map to a state via USPS sectional center prefixes. The calculator uses the state median — not an exact well measurement for your address.
- USGS source data. State medians are derived from the USGS National Water-Quality Assessment Program and published water utility Consumer Confidence Reports. High-plains states (KS, NE, SD, AZ, ND) typically exceed 17 GPG; New England states (ME, VT, NH, MA) average under 4 GPG.
- When to test directly. Private wells and some municipal blends vary significantly within a state. For an exact reading, request your utility's Consumer Confidence Report (free by law) or buy a $15 test strip kit.
Data provenance: methodology page.
What else do people ask about water hardness?
What counts as "hard" water?
Water above 7 grains per gallon (GPG) is considered hard. At that level, calcium carbonate scale starts depositing inside water heaters, reducing thermal efficiency.
How much does hard water actually affect my water heater?
A University of New Mexico study found that a standard tank water heater loses roughly 1.5% efficiency per GPG of hardness over its lifespan. At 18 GPG, found in states like Kansas, Nebraska, and Arizona, that works out to about 27% efficiency loss.
How accurate is the ZIP lookup for my exact address?
It uses the state median hardness value, not an exact measurement for your address. Private wells and some municipal blends vary significantly within a state.
Which states tend to have the hardest and softest water?
High-plains states such as Kansas, Nebraska, South Dakota, Arizona, and North Dakota typically exceed 17 GPG, while New England states such as Maine, Vermont, New Hampshire, and Massachusetts average under 4 GPG.
How can I get an exact hardness reading for my address?
Request your water utility's Consumer Confidence Report, which is free by law, or test your water directly with a strip kit.
Sources
Want the real number for your house? A licensed plumber gives you a written estimate by phone — free, no obligation.