Radon Level Risk Calculator
Assess your radon exposure risk based on measured radon levels.
Understand EPA action levels and when to mitigate radon in your home.
Radon is a naturally occurring radioactive gas produced by the decay of uranium in soil and rock. It is colorless, odorless, and tasteless — you cannot detect it without a test. Radon is the #2 cause of lung cancer in the United States, responsible for approximately 21,000 deaths per year.
How radon enters homes:
Radon seeps up from the ground through cracks in foundations, floor drains, and construction joints. It accumulates in enclosed spaces — especially basements and ground-floor areas with poor ventilation. Upper floors typically have lower radon levels than ground floors and basements.
Radon measurement units:
- pCi/L (picocuries per liter), used in the United States
- Bq/m³ (becquerels per cubic meter), used in Europe and internationally
- Conversion: 1 pCi/L = 37 Bq/m³
EPA radon action levels:
| Radon Level | EPA Guidance |
|---|---|
| Under 2 pCi/L | Average indoor radon (2.7 pCi/L is US average), no action required |
| 2–4 pCi/L | Below action level, but mitigation should be considered |
| 4 pCi/L+ | EPA action level, fix your home |
| 8–10 pCi/L | High, significant health risk, prioritize mitigation |
| Above 20 pCi/L | Very high, take immediate action |
Lifetime cancer risk estimates (smokers vs non-smokers):
Radon and smoking are a particularly dangerous combination — the risks multiply, not just add.
| Radon Level | Lifetime Risk (never-smoker) | Lifetime Risk (smoker) |
|---|---|---|
| 2 pCi/L | 2.5 in 1,000 | 32 in 1,000 |
| 4 pCi/L | 5 in 1,000 | 62 in 1,000 |
| 8 pCi/L | 10 in 1,000 | 120 in 1,000 |
| 20 pCi/L | 36 in 1,000 | 260 in 1,000 |
Radon mitigation:
The most common solution is sub-slab depressurization (ASD): A pipe is inserted through the floor slab and a fan draws radon out from under the house before it enters the living space. Cost: typically $800–$2,500 for a professional installation. This reduces radon by 50–99% in most homes.
Testing:
- Short-term tests (2–7 days): Use a charcoal canister from a hardware store (~$15–$25)
- Long-term tests (90+ days): More accurate seasonal average
- Professional testing: $100–$300
- Test every 2 years, or after major renovations or changes in HVAC system
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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