How accurate is a radon estimate by ZIP code?

It's a county-level average, not a reading for your specific home. Radon varies house to house even on the same street, so a ZIP lookup tells you the risk profile of your area — how often tested homes nearby come back over the 4 pCi/L action level. The only way to know your home is to test it.

Where does the ZIP radon data come from?

We map your ZIP to its primary county, then show that county's radon test statistics from the CDC's national tracking dataset (CDC EPHT (labs), 2008–2017). Every figure shows the number of tests behind it. See our methodology page for full sourcing.

My ZIP shows no data — what does that mean?

It means no aggregated radon tests were reported for that county in the national dataset — not that radon is absent. Radon is present to some degree almost everywhere. Test your home to know for certain.

Instant lookup

Radon levels by ZIP code

Type your ZIP and see how radon tests up in your county — the share over the EPA action level, the median, the range. Real data, no email, no waiting.

Enter your ZIP code

Instant — no email, no waiting. Type 5 digits and we'll show your county's measured radon levels.

How do we get all this testing data?

The radon levels here aren’t estimates or models — they’re aggregated from real home radon tests. Here’s the journey every number takes:

A homeowner testsSomeone places a radon test kit in the lowest lived-in level of their home for a few days — a lab-grade charcoal kit that runs about $15–$30 retail, shipping and analysis included.
The kit is mailed to a labThey seal it and send it off. Because radon decays quickly, the kit has to reach the lab within days of finishing the test.
A scientist analyzes itThe lab measures the radioactivity captured on the charcoal and calculates the home's radon level in pCi/L.
The result becomes dataThe homeowner gets their number — and the lab reports the (anonymized) result to state and federal health agencies. Millions of those results, pooled by county, are the CDC dataset behind every number on this site.

That’s why we can show a real percentage for your county — and why we always show how many tests it’s based on. See the full methodology.

What the number means

The headline figure is the percent of tested homes in your county that read at or above 4 pCi/L — the EPA’s action level, the point at which it recommends installing a mitigation system. If a county shows 45%, nearly half of the homes that were tested there came back high enough to warrant mitigation. That’s a measure of how radon-prone the area is, drawn from real tests — not a prediction for your specific address.

Radon seeps from soil and rock, so it varies with local geology and, house by house, with foundation type and construction. Two homes next door can read very differently. Use the county number to understand your risk; use a test kit to know your home.

All figures come from the CDC’s national radon tracking data (CDC EPHT (labs), 2008–2017), and every county shows the number of tests behind it. Where a state publishes fresher data, we use it and say so — see the methodology. Want the cost side? Browse by state for mitigation-cost guides.

Common questions

How accurate is a radon estimate by ZIP code?: It's a county-level average, not a reading for your specific home. Radon varies house to house even on the same street, so a ZIP lookup tells you the risk profile of your area — how often tested homes nearby come back over the 4 pCi/L action level. The only way to know your home is to test it.
Where does the ZIP radon data come from?: We map your ZIP to its primary county, then show that county's radon test statistics from the CDC's national tracking dataset (CDC EPHT (labs), 2008–2017). Every figure shows the number of tests behind it. See our methodology page for full sourcing.
My ZIP shows no data — what does that mean?: It means no aggregated radon tests were reported for that county in the national dataset — not that radon is absent. Radon is present to some degree almost everywhere. Test your home to know for certain.