Radioactivity Converter
Same value in every unit
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Activity is not dose
A becquerel is one decay per second. It describes the source — how busy it is — and says nothing about what reaches a person. Absorbed dose is measured in gray and equivalent dose in sievert, and neither can be worked out from becquerel alone. It depends on the type of radiation, the distance, the shielding, and whether the material is outside the body or has been taken into it.
This page converts activity units. It is not a dose calculator and it is not a safety assessment.
The two systems
The becquerel is the SI unit and is used almost everywhere. The curie is older, defined as exactly 37 billion becquerel — originally the activity of a gram of radium-226 — and remains common in the United States. A megabecquerel is about 27 microcurie, which is why laboratory labels so often need converting.
Where you meet these numbers
- Nuclear medicine — an injected tracer might be a few hundred megabecquerel
- Food and water limits — becquerel per kilogram or per litre
- Laboratory sources — often labelled in microcurie
- Environmental surveys — becquerel per cubic metre for radon
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Frequently Asked Questions
One nuclear decay per second. It says how active a source is, not how much radiation anybody absorbs — that is dose, measured in gray and sievert, which are different quantities entirely and are not convertible from these.
Exactly 37 billion, by definition — the curie was originally set to the activity of one gram of radium-226. It is a large unit, which is why medical and laboratory work is usually quoted in megabecquerel or millicurie.
Not on its own. Risk depends on what is decaying, what kind of radiation it emits, whether it is inside or outside you, and for how long. A large number of very weak decays can matter far less than a small number of energetic ones.
Nuclear medicine doses, food and water contamination limits, laboratory source labels and environmental surveys. Becquerel is the SI unit and dominates outside the United States; curie persists in American practice.
No. This converts units and nothing more. Anything concerning exposure or safety belongs with a qualified radiation protection professional.