Radioactivity Converter
Convert radioactivity units in seconds, from becquerels to curies, millicuries, nanocuries, disintegrations per second, and rutherfords.
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What this converter does
Radioactivity is measured by how fast something decays, the number of atomic nuclei breaking down each second. This converter moves a value between the units for that decay rate: the becquerel used in science today, the older curie, and their many prefixed forms. One thing to be clear about from the start: these are units of activity, the rate of decay, not units of radiation dose or exposure, which are a separate matter.
How to use it
Enter the activity, pick the unit you have under From and the unit you want under To, and press Calculate. It opens on becquerels to kilobecquerels. Swap reverses the two, Reset clears the field, and the result is shown to nine significant figures.
How it works
The becquerel is the base, defined as one decay per second, so the disintegrations-per-second and one-per-second entries are simply other names for it. Everything else is a multiple: a curie is 37 billion becquerels, a rutherford is one million. The tool converts your value to becquerels and then out to the unit you want.
Common radioactivity conversions
The ones that come up most:
| Conversion | Value |
|---|---|
| 1 becquerel (Bq) | 1 decay per second |
| 1 curie (Ci) | 37,000,000,000 Bq (37 GBq) |
| 1 millicurie (mCi) | 37,000,000 Bq (37 MBq) |
| 1 microcurie (µCi) | 37,000 Bq (37 kBq) |
| 1 rutherford (Rd) | 1,000,000 Bq (1 MBq) |
| 1 Bq | about 27 picocuries (pCi) |
Becquerel, curie, and what activity measures
Two units do most of the work here, and they differ enormously in size.
The becquerel (Bq) is the SI unit, named after Henri Becquerel, who discovered radioactivity. It is tiny: one decay per second. Because real samples decay thousands or millions of times a second, you usually see it with a prefix, like kBq or MBq.
The curie (Ci) is the older unit, named after Marie and Pierre Curie, and it is huge by comparison: one curie is 37 billion becquerels, roughly the activity of a gram of radium. It is still common in the United States, where sources are often quoted in microcuries or millicuries. The rutherford (Rd), equal to one million becquerels, is an older unit you will rarely meet now. For a sense of scale, many household smoke detectors contain a tiny americium source with an activity around 37 kilobecquerels, or about one microcurie., which is around one microcurie.
A word on what these units do and do not tell you. Activity counts how many nuclei decay each second. On its own it says nothing about how much energy those decays carry, what kind of radiation comes off, or the dose a person would receive, all of which depend on the material and the circumstances. Activity and dose are different quantities with different units, and this tool handles activity.
Questions people ask
What is a becquerel?
The SI unit of radioactivity, equal to one decay per second. It is named after Henri Becquerel, who discovered radioactivity in 1896.
How many becquerels are in a curie?
37 billion, written 3.7 × 10¹⁰ Bq, which is also 37 gigabecquerels. The curie is a much larger unit than the becquerel.
What is the difference between activity and dose?
Activity is the rate at which a material decays, measured in becquerels or curies, which is what this tool converts. Dose is about the energy radiation deposits and its effect on tissue, measured in separate units. The two are not interchangeable.
Why is the curie so much larger than the becquerel?
Because the curie was originally based on the activity of one gram of radium, which decays about 37 billion times a second. The becquerel, by contrast, is just a single decay per second.
What is a rutherford?
An older unit of activity equal to one million becquerels, or one megabecquerel. It is rarely used today, having been replaced by the becquerel.
References
- National Institute of Standards and Technology (NIST), Office of Weights and Measures. The International System of Units (SI) and the becquerel. https://www.nist.gov/pml/owm/metric-si/si-units
Okan Atalay is a results driven senior operations manager and a graduate of Industrial Engineering from Bilkent University. With over 22 years of experience in textile manufacturing and integrated operations, he has led large scale business process improvements and strategic planning initiatives. Currently, he serves as a top mathematics expert for a global ed tech platform, where he applies his analytical expertise to solve complex mathematical problems. At Eon Tools, he reviews converter and maths tools.