☢️ Radioactivity Unit Converter
Convert between becquerel (Bq), curie (Ci), and related units of radioactivity (decays per second) in real time. One curie is defined as exactly 3.7×10^10 becquerels.
How to use
- Enter a value in the unit you want to convert from.
- The converted values in the other units update in real time.
How the calculation works
This tool converts between units of radioactivity — the number of nuclear decays (nuclei emitting radiation and changing into other nuclei) per second. The SI unit, the becquerel (Bq), is one decay per second. The curie (Ci) is an older unit originally based on the activity of one gram of radium-226, and is now defined as exactly 3.7 × 10¹⁰ Bq (37 billion becquerels). The tool converts the value you enter to becquerels first, then to each of the other units. The prefixes mean: kilo (k) × 1000, mega (M) × 1 million, giga (G) × 1 billion, milli (m) ÷ 1000 and micro (µ) ÷ 1 million.
Worked example
1 Ci = 37,000,000,000 Bq = 37 GBq 1 mCi = 37,000,000 Bq = 37 MBq 1 µCi = 37,000 Bq = 37 kBq Conversely, 1 MBq = 1,000,000 ÷ 37,000 ≈ 27.03 µCi. Doses of radiopharmaceuticals in nuclear medicine are often given in MBq in Japan and Europe and in mCi in the US, so this conversion comes up often.
Things to be aware of
- Activity (Bq) and radiation dose to people (sieverts, Sv) are different quantities and cannot be converted with a simple factor.
- Limits for radioactive substances in food are given in Bq/kg (becquerels per kilogram). Converting the unit here does not change the reference amount such as "per kg".
- Activity decreases over time (half-life). This tool only converts units at a single point in time.
FAQ
What’s the relationship between becquerel and curie?
One curie (Ci) is defined as exactly 3.7×10^10 becquerels (Bq) — a historical value based on the decay rate of 1 gram of radium-226.
Which unit is the modern one?
The becquerel (Bq) is the official SI unit, representing one decay per second. The curie (Ci) is an older, traditional unit still used in some fields.
Can this calculate radiation dose (sieverts)?
No. Radioactivity (decay rate) and radiation dose (absorbed/equivalent dose) are different physical quantities that can’t be converted with a simple factor, so this tool doesn’t cover dose.