Tools
Free tools
Three free tools built on EPA’s published radon zone data and testing guidance.
Radon zone lookup by ZIP
Enter a ZIP code to see the county (or counties) it falls in and each county’s EPA radon zone, with the data source and date.
Open the tool →Radon level calculator
Enter a test result in pCi/L or Bq/m³. See how it compares with the EPA action level, the WHO reference level, and the U.S. average.
Open the tool →Radon follow-up test planner
Got a first test back? Answer three questions and get EPA’s recommended next step: retest, long-term test, or fix.
Open the tool →How our tools work
The ZIP lookup uses EPA’s county zone data and the Census Bureau’s 2020 ZCTA-to-county relationship file, both public. Inferred zones (for counties not listed on the 1993 map) are labeled. The level calculator uses the conversion 1 pCi/L = 37 Bq/m³ and EPA’s published action levels.
Start with the ZIP lookup to see your county’s EPA radon zone. Remember what EPA says about its own map: it was built in 1993 to help governments target resources, and it should not be used to decide whether a single home needs testing. Every home should be tested, whatever the zone.
When your test result comes back, the level calculator converts units and puts your number next to EPA’s action level of 4 pCi/L and the ‘consider fixing’ range of 2 to 4 pCi/L. The follow-up planner then walks through EPA’s decision steps for a first short-term result, so you know whether to retest, run a long-term test, or call a qualified mitigation contractor. None of the tools replace a test: they help you understand the number a test gives you.
Nothing you type into a tool is saved on our servers unless the tool says so. Letter builders and checklists run entirely in your browser.