Radioactivity Converter

Radioactivity measures how many atomic nuclei in a sample decay each second. The SI unit is the becquerel (Bq): one becquerel is one decay per second. It’s a count of events and nothing more, which is the root of a lot of confusion about what these numbers actually mean for safety.

Metric prefixes:

• 1 kBq = 1,000 Bq
• 1 MBq = 1,000,000 Bq

Legacy unit (curie):

• 1 Ci = 3.7 × 10¹⁰ Bq (37 billion Bq)
• 1 mCi = 37 MBq

For scale:

• A banana: about 15 Bq (natural potassium-40)
• A human body: about 7,000 Bq
• A medical imaging dose: 100–700 MBq

The curie is huge because it was originally tied to the activity of one gram of radium. A full curie is a serious amount of radioactivity, so modern work almost always uses becquerels or the milli- and microcurie.

Here’s the point people miss: becquerels measure decays, not harm. Your own body ticks along at about 7,000 Bq every second of your life and is perfectly fine. The type of radiation, its energy, and whether the source sits inside or outside you all matter. The unit that captures biological harm is the sievert, an entirely separate measurement. A big becquerel figure on its own tells you nothing about danger.