Radiation-Activity Converter
Convert between radioactivity (source activity) units — becquerel, kilobecquerel, megabecquerel, curie, millicurie, microcurie, picocurie, rutherford, and disintegrations per second or minute.
Results from this calculator are estimates provided for general informational purposes only, based on formulas, rates, and standards commonly accepted as of 2026. Figures may differ slightly from other calculators or professional sources due to rounding methods, differing assumptions, or regional regulations, and rules may change over time. Always consult a qualified professional — such as a financial advisor, healthcare provider, or other relevant specialist — before making decisions based on these results.
Result
1 Bq = 2.7027E-11 Ci
1 Becquerel = 2.7027E-11 Curies
1 Curie = 3.7E+10 Becquerels
1 Bq in every supported unit
What is a Radiation-Activity Converter?
This converter measures activity — how radioactive a source of material is, counted as decays (disintegrations) per second. Its SI unit is the becquerel (Bq), defined as exactly one decay per second, a deliberately small and intuitive unit. Activity is a property of the material itself: a chunk of radioactive isotope has a certain activity in becquerel or curie regardless of whether anyone or anything is standing nearby to absorb the radiation it emits. The curie (Ci), the older and far larger CGS unit equal to 37 billion decays per second, remains common in US medical and industrial contexts — real-world sources are usually quoted in milli- or microcuries precisely because a whole curie is such an enormous number of decays per second.
Activity is easy to confuse with the other three radiation quantities in this wave, so it's worth being explicit: activity (this converter) describes the source alone, independent of distance or shielding; dose rate describes how fast energy is actually being absorbed by something near that source, which depends on distance, shielding, and radiation type as well as the source's activity; exposure describes ionization specifically produced in air by X-rays or gamma rays; and absorbed dose is a cumulative total of energy absorbed. A highly active source that's far away or well shielded can deliver a very low dose rate — activity alone never tells you how much radiation reaches a person.
Conversion chart: Becquerel to Curies
Conversion table
| Becquerel (Bq) | Curie (Ci) |
|---|---|
| 0.01 Bq | 2.7027E-13 Ci |
| 0.1 Bq | 2.7027E-12 Ci |
| 1 Bq | 2.7027E-11 Ci |
| 2 Bq | 5.40541E-11 Ci |
| 3 Bq | 8.10811E-11 Ci |
| 5 Bq | 1.35135E-10 Ci |
| 10 Bq | 2.7027E-10 Ci |
| 20 Bq | 5.40541E-10 Ci |
| 50 Bq | 1.35135E-09 Ci |
| 100 Bq | 2.7027E-09 Ci |
| 1000 Bq | 2.7027E-08 Ci |
Supported Units
| Unit | Symbol | In Bq |
|---|---|---|
| Becquerel | Bq | 1 Bq |
| Terabecquerel | TBq | 1E+12 Bq |
| Gigabecquerel | GBq | 1E+09 Bq |
| Megabecquerel | MBq | 1000000 Bq |
| Kilobecquerel | kBq | 1000 Bq |
| Millibecquerel | mBq | 0.001 Bq |
| Curie | Ci | 3.7E+10 Bq |
| Kilocurie | kCi | 3.7E+13 Bq |
| Millicurie | mCi | 37000000 Bq |
| Microcurie | µCi | 37000 Bq |
| Nanocurie | nCi | 37 Bq |
| Picocurie | pCi | 0.037 Bq |
| Rutherford | Rd | 1000000 Bq |
| One/Second | 1/s | 1 Bq |
| Disintegrations/Second | dis/s | 1 Bq |
| Disintegrations/Minute | dis/min | 0.016666667 Bq |
About These Parameters
- Value
- The activity you want to convert, expressed in the "From" unit. Accepts decimals, and can represent anything from a trace laboratory tracer in nanocuries to an industrial gamma-radiography source in terabecquerels.
- From Unit
- The unit your activity figure is currently measured in — a nuclear-medicine dose sheet's millicuries, an environmental report's becquerels per kilogram, or an older physics text's rutherfords.
- To Unit
- The unit you want the result converted into. Use the swap button to flip From and To instantly, which is handy when translating a US clinical curie figure into the modern SI becquerel or vice versa.
How Radioactivity Conversion Works
The Formula
Every unit here is defined by a fixed multiplier relative to the becquerel. To convert a value from one unit to another:
result = value × (factor of "From" unit ÷ factor of "To" unit)
For Becquerel → Curie: multiply by 2.7027E-11. For example, 1 Bq × 2.7027E-11 = 2.7027E-11 Ci.
Why the Curie Is Still Everywhere Despite Becquerel Being the SI Standard
The curie was defined in the early 20th century as the activity of exactly one gram of radium-226 — a huge number of decays per second (37 billion) that happened to match the quantities researchers were actually handling at the time. When the SI adopted the becquerel in 1975 as a deliberately small, easy-to-reason-about unit (one decay per second), it created a scale mismatch: real sources that were "1 curie" became "37 billion becquerel," an awkward number to say or write. US medical and industrial practice never fully switched over, which is why millicuries and microcuries still dominate American clinical paperwork even as the rest of the world reports in kilobecquerels and megabecquerels.
Activity Is Not the Same as Dose
A source's activity tells you how many atoms are decaying every second, but says nothing about how much of that radiation actually reaches and is absorbed by a person or object — that depends on distance (radiation intensity falls off with distance), shielding, and the type of radiation being emitted (alpha particles barely penetrate skin; gamma rays pass through substantial shielding). A one-curie source sealed behind thick lead delivers a far lower dose rate than the same source held in an open hand. That's why radiation-safety training treats activity and dose rate as two separate numbers that must both be known, never one inferred from the other.
Example
An activity of 1 Bq equals 2.7027E-11 Ci. For scale, a typical nuclear-medicine diagnostic dose is a few hundred megabecquerels (roughly 10-30 millicuries), household smoke detectors contain an americium-241 source of about 1 microcurie (37,000 becquerels), and industrial radiography sources used for inspecting welds commonly run several terabecquerels (tens to hundreds of curies).
Frequently Asked Questions
What's the difference between a becquerel and a curie?
Both measure activity (decays per second), but on very different scales. One becquerel is exactly one decay per second; one curie is 37 billion decays per second — the activity originally defined as one gram of radium-226. Because the curie is so large, real sources are usually quoted in millicuries or microcuries, while becquerel figures are more often scaled up with mega- or giga- prefixes.
Does higher activity always mean higher radiation exposure?
Not necessarily. Activity only describes the source's own decay rate — the actual dose someone receives also depends on distance from the source, shielding in between, exposure time, and the type of radiation emitted. A highly active but well-shielded or distant source can deliver a lower dose rate than a much less active source held close by. See the separate Radiation Converter for dose rate specifically.
What is the rutherford and why isn't it used anymore?
The rutherford, named after physicist Ernest Rutherford, was a mid-20th-century unit equal to one million decays per second — a middle ground between becquerel and curie. It never gained wide international adoption and was effectively abandoned once the SI standardized on the becquerel in 1975, so it now appears only in older physics literature.
Why are disintegrations/minute used instead of disintegrations/second in some labs?
Liquid-scintillation counters and similar laboratory instruments historically reported raw counts on a per-minute basis, matching typical counting-run durations, so biochemistry and radiochemistry labs still commonly report activity in disintegrations (or counts) per minute rather than converting to the SI per-second convention.