Radiation-Activity Converter
Convert radioactive activity between becquerel and its multiples, curie and its submultiples, rutherford, disintegrations per second and disintegrations per minute. Pick two units, enter a value and read the result instantly.
Select two units to see the conversion factor.
Activity counts decays per second. It is not a dose or exposure and cannot be converted into one without more information. This is a unit converter, not a safety or medical assessment.
Radioactivity Formula
Every activity unit is a fixed multiple of one reference unit, the becquerel (1 Bq = 1 decay per second). To convert, multiply the value by the size of the source unit in Bq, then divide by the size of the target unit in Bq. The curie is defined as exactly 3.7 × 10¹⁰ Bq, the rutherford as 10⁶ Bq and the disintegration per minute as 1/60 Bq. SI prefixes are exact powers of ten.
What Is Radioactive Activity?
Activity is the number of nuclear decays (disintegrations) that occur in a radioactive sample per unit of time. In symbols A = dN/dt, and for a single radionuclide A = λN, where N is the number of radioactive nuclei and λ the decay constant. The SI unit is the becquerel (Bq), equal to one decay per second, named after Henri Becquerel. A kilobecquerel is 1,000 decays per second, a megabecquerel one million and a gigabecquerel one billion.
The traditional unit is the curie (Ci). It was originally the activity of one gram of radium-226 and is now defined exactly as 3.7 × 10¹⁰ decays per second, so 1 Ci = 37 GBq. Because that is a very large activity, millicuries (mCi), microcuries (µCi) and picocuries (pCi) are common in medicine and in environmental measurements. The rutherford (Rd), equal to 10⁶ decays per second, is an obsolete unit. Count-rate meters often read disintegrations per minute (dpm).
Activity tells you how many nuclei decay, but not how much energy is deposited in matter or what biological effect results. Those depend on the type and energy of the radiation, the distance, the shielding and the absorbing material. For that reason activity is never converted directly into absorbed dose (gray, rad), exposure (C/kg, roentgen) or equivalent dose (sievert, rem). Turning activity into the number of atoms or a mass needs the half-life and the atomic mass of the radionuclide and is also outside this converter.
Supported Units
This converter supports the following 16 activity units. The last column shows how many becquerel one unit equals. The values are exact, with the curie defined as 37 billion becquerel.
| Unit | Symbol | Value in Bq |
|---|---|---|
| Becquerel | Bq | 1 |
| Terabecquerel | TBq | 1e+12 |
| Gigabecquerel | GBq | 1,000,000,000 |
| Megabecquerel | MBq | 1,000,000 |
| Kilobecquerel | kBq | 1,000 |
| Millibecquerel | mBq | 0.001 |
| Curie | Ci | 37,000,000,000 |
| Kilocurie | kCi | 3.7e+13 |
| Millicurie | mCi | 37,000,000 |
| Microcurie | µCi | 37,000 |
| Nanocurie | nCi | 37 |
| Picocurie | pCi | 0.037 |
| Rutherford | Rd | 1,000,000 |
| One per second | 1/s | 1 |
| Disintegrations per second | dps | 1 |
| Disintegrations per minute | dpm | 0.01666666667 |
How to Use the Radiation-Activity Converter
- Type the activity in the value box. Decimals and scientific notation such as 0.0025 or 2.5e-3 are accepted.
- Choose the From unit and the To unit.
- The result appears instantly, or press Convert Now. Very large or very small results are shown in scientific notation.
- Use Swap Units to reverse the conversion, Copy Result to copy the answer, open Show this value in all units for a full list, and Clear to start again.
Step-by-step by hand
- Find the size of each unit in the common base unit (Bq): 1 Ci = 37,000,000,000 Bq and 1 GBq = 1,000,000,000 Bq.
- Divide the source size by the target size to get the conversion factor: 37,000,000,000 ÷ 1,000,000,000 = 37, so 1 Ci = 37 GBq.
- Multiply by your value: 1 Ci × 37 = 37 GBq.
Activity cannot be negative, so only zero and positive numbers are accepted.
Common Activity Conversions
- The curie: 1 Ci equals 37,000,000,000 Bq, which is 37 GBq.
- Nuclear medicine: a 10 mCi dose equals 370 MBq, and 370 MBq equals 10 mCi.
- Small sealed sources: 1 µCi equals 37 kBq.
- Environmental samples: 4 pCi equals 148 mBq, which is 0.148 Bq.
- Count rates: 600 dpm equals 10 Bq.
- Obsolete unit: 5 rutherford equals 5 MBq.
- Large source: 2 kCi equals 74 TBq.
Curie to Becquerel – Common Values
Quick reference for frequently used values
| Curie (Ci) | Becquerel (Bq) | Gigabecquerel (GBq) | Megabecquerel (MBq) | Terabecquerel (TBq) |
|---|---|---|---|---|
| 1e-6 | 37,000 | 3.7e-5 | 0.037 | 3.7e-8 |
| 0.001 | 37,000,000 | 0.037 | 37 | 3.7e-5 |
| 0.01 | 370,000,000 | 0.37 | 370 | 0.00037 |
| 0.1 | 3,700,000,000 | 3.7 | 3,700 | 0.0037 |
| 1 | 37,000,000,000 | 37 | 37,000 | 0.037 |
| 5 | 185,000,000,000 | 185 | 185,000 | 0.185 |
| 10 | 370,000,000,000 | 370 | 370,000 | 0.37 |
| 100 | 3.7e+12 | 3,700 | 3,700,000 | 3.7 |
| 1,000 | 3.7e+13 | 37,000 | 37,000,000 | 37 |
Where and Why This Conversion Is Used
- Nuclear medicine: radiopharmaceutical activities are given in MBq or mCi depending on the country and the supplier.
- Radiation protection and licensing: source inventories and exemption levels are listed in Bq, kBq, MBq or Ci.
- Environmental monitoring: radon and fallout concentrations are reported in Bq or pCi per unit of volume or mass.
- Industry and research: calibration sources, gauges and tracers are labelled in µCi or kBq.
- Laboratory counting: counter results in dpm are compared with Bq values on certificates.
Important Differences Between Related Radiation Measurements
- Activity (Bq, Ci): decays per second in a source.
- Exposure (C/kg, R): ionization caused in air by X-rays or gamma rays.
- Absorbed dose (Gy, rad): energy absorbed per kilogram of material.
- Equivalent and effective dose (Sv, rem): absorbed dose weighted for radiation type and tissue sensitivity.
A source of a given activity can deliver very different doses depending on distance, shielding and the radiation emitted, so these quantities are not interchangeable. See the Radiation-Absorbed Dose Converter, the Radiation-Exposure Converter and the Radiation Converter for the others.
Educational disclaimer: this page converts units of measurement only. The results are not a radiation-safety assessment, a dose estimate for a person or a medical opinion, and they should not replace advice from a qualified radiation-safety officer, medical physicist or physician.