You can get a rough answer for your area in minutes and the real answer for your house in a day. The rough answer comes from a hardness map or your utility's annual report; the real answer comes from testing water at your own tap, which is the only figure anyone should size equipment from.
The bands, and what they mean for you
The USGS describes hardness as dissolved calcium and magnesium and classifies it as calcium carbonate: soft is 0 to 60 mg/L, moderately hard is 61 to 120, hard is 121 to 180, and very hard is more than 180 mg/L. Softener capacity is usually quoted in grains per gallon instead, and laboratories will report either. Knowing your band tells you whether scaling and soap curd are likely to be your problem at all before you go looking for equipment.
Three ways to look it up
First, national hardness maps show the general picture for your region, which is enough to know whether hard water is plausible where you live. Second, if you are on a municipal supply, the annual Consumer Confidence Report or a call to the utility gives the treated water figure for your system. Third, a home titration kit or a laboratory test gives your tap. Each answer is narrower and more useful than the last, and only the third accounts for your own plumbing and any blending between sources.
Why the area figure is not your figure
Utilities blend sources seasonally, so hardness can change through the year. Neighborhoods on different mains within one system can differ. Private wells vary street by street with the geology, and two houses on the same road can test far apart. A softener sized from a map instead of a measurement will either regenerate more often than it needs to, wasting salt and water, or fail to keep up and let hard water slip through toward the end of a cycle.
Testing your own tap properly
Draw from a cold tap that is not fed through any existing treatment, run it for a minute first, and use a titration kit rather than a strip if you want a number you can size from. If you already have a softener, test both the raw inlet and the treated outlet so you know its true starting point and whether it is still working. Retest after any change in your supply. Our water hardness testing guide covers laboratory options if you want a formal result.
Questions people ask about water hardness in my area
How do I find my water hardness for free?
Check your utility's annual Consumer Confidence Report or call them. On a well, only a test kit or laboratory result will give a real figure.
Is a test strip accurate enough to size a softener?
Strips give a band, not a number. Use a titration kit or a laboratory result, since sizing depends on the actual grains per gallon.
Can hardness change during the year?
Yes. Utilities blend sources seasonally and well levels shift, so a figure taken once can drift. Retest if scaling suddenly gets worse.
Does hard water need treating at all?
It is an aesthetic and plumbing issue rather than a health one, so treat it when scaling, soap curd and appliance wear are actually bothering you.