Radon unit converter: pCi/L and Bq/m³
To convert a radon reading, multiply picocuries per litre by 37 to get becquerels per cubic metre, or divide Bq/m³ by 37 to get pCi/L. Canada reports radon in Bq/m³ and sets its guideline at 200 Bq/m³, which is about 5.4 pCi/L. The United States uses pCi/L and an action level of 4 pCi/L, about 148 Bq/m³. Type a number in either box below and the other unit appears.
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Convert a radon reading
Type a value in either box.
How do you convert pCi/L to Bq/m³?
Multiply by 37. One picocurie per litre is equal to 37 becquerels per cubic metresource. A monitor showing 3.0 pCi/L is therefore reporting 111 Bq/m³, and one showing 6.0 pCi/L is reporting 222 Bq/m³. To go the other way, divide: 300 Bq/m³ divided by 37 is about 8.1 pCi/L.
The factor is exact because both units count the same thing, radioactive decays in a volume of air, on different scales. A becquerel is one decay per second. A picocurie is a much older unit based on the activity of radium, and a litre is a thousandth of a cubic metre. Put the two together and the ratio comes to 37.
What are the common values in both units?
The two tables cover the readings people most often need to translate. Bq/m³ values are rounded to the nearest whole number and pCi/L values to one decimal place.
| pCi/L | Bq/m³ | Where it sits |
|---|---|---|
| 1 pCi/L | 37 Bq/m³ | Below the Canadian guideline |
| 2 pCi/L | 74 Bq/m³ | Below the Canadian guideline |
| 2.7 pCi/L | 100 Bq/m³ | WHO reference level |
| 4 pCi/L | 148 Bq/m³ | US EPA action level |
| 5.4 pCi/L | 200 Bq/m³ | Canadian guideline |
| 8 pCi/L | 296 Bq/m³ | Above the Canadian guideline |
| 10 pCi/L | 370 Bq/m³ | Above the Canadian guideline |
| 16.2 pCi/L | 599 Bq/m³ | Above the Canadian guideline |
| 20 pCi/L | 740 Bq/m³ | Above the Canadian guideline |
| Bq/m³ | pCi/L | Where it sits |
|---|---|---|
| 50 Bq/m³ | 1.4 pCi/L | Below the Canadian guideline |
| 100 Bq/m³ | 2.7 pCi/L | WHO reference level |
| 148 Bq/m³ | 4.0 pCi/L | US EPA action level |
| 200 Bq/m³ | 5.4 pCi/L | Canadian guideline |
| 300 Bq/m³ | 8.1 pCi/L | Above the Canadian guideline |
| 400 Bq/m³ | 10.8 pCi/L | Above the Canadian guideline |
| 600 Bq/m³ | 16.2 pCi/L | Above the Canadian guideline |
| 800 Bq/m³ | 21.6 pCi/L | Above the Canadian guideline |
| 1,000 Bq/m³ | 27.0 pCi/L | Above the Canadian guideline |
Which unit does Canada use?
Becquerels per cubic metre. Health Canada's guideline is written as 200 Bq/m³source, Canadian laboratories report in that unit, and so does this site. In American units the guideline is about 5.4 pCi/Lsource. If you are reading a Canadian report, no conversion is needed.
The three reference levels you will see quoted are easy to mix up when units are mixed: the US EPA's action level of 4 pCi/L is about 148 Bq/m³source, and the World Health Organization's reference level is 100 Bq/m³source, which is 2.7 pCi/L. Lined up in one unit they read 100, 148 and 200 Bq/m³.
Why would a reading in Canada be in pCi/L?
Usually because the device was built for the American market. Many consumer monitors and some mail-in kits sold online display pCi/L by default, and their built-in alerts are set to the US action level. Most monitors let you switch to Bq/m³ in the settings or the phone app, which is worth doing once so that every later reading can be compared with the Canadian guideline at a glance.
Home inspection reports from the United States, relocation paperwork and American websites are the other common sources. A number such as "4.0" with no unit beside it is almost always in pCi/L.
What mistakes do people make when converting?
- Comparing a pCi/L number with 200. A reading of 6 looks tiny beside 200 until it is converted to 222 Bq/m³.
- Treating 4 pCi/L as the Canadian threshold. It is the American one. The Canadian guideline sits at about 5.4 pCi/L.
- Converting a single reading and stopping there. The unit is only half of what matters; the other half is how long the test ran.
- Rounding too early. Convert first, then round, especially for results near the guideline.
On the third point: Health Canada recommends a test of three to twelve months, and no less than 91 dayssource, and the guideline applies to that long-term average. Once your number is in Bq/m³, the radon test result checker takes the length and type of test into account, and our page on radon levels and the Canadian guideline explains what each range calls for. If you do not have a long-term result yet, radon testing in Calgary shows how to get one.
Frequently asked questions
What is a becquerel per cubic metre?
A becquerel is one radioactive decay per second. Bq/m³ counts how many radon decays happen each second in one cubic metre of air. Canada, the WHO and most countries use it; the US uses picocuries per litre (pCi/L).
Why does my monitor show pCi/L?
Some consumer monitors default to pCi/L, the unit used in the US. Many let you switch units in the settings; check the manual. Either way, 1 pCi/L equals 37 Bq/m³.
What is 4 pCi/L in Bq/m³?
About 148 Bq/m³. That's the US EPA action level, and it sits below Canada's 200 Bq/m³ guideline. A Canadian home at 4 pCi/L is under the Canadian guideline but well above the WHO reference of 100 Bq/m³.
What is 300 Bq/m³ in pCi/L?
About 8.1 pCi/L. That's 1.5 times Canada's guideline and calls for mitigation within a year under Health Canada's guidance.
Sources
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