Radiation-Activity Converter
Print pageAll Equivalents Reference Table
| Unit | Equivalent Value |
|---|
Radioactive activity (symbolized by A) measures the rate of nuclear decay in a sample of unstable radioactive atoms, expressed as the number of atomic nuclei undergoing spontaneous disintegration per unit of time (A = -ΔN / Δt). In nuclear medicine, radiopharmacy, environmental radon testing, and health physics, radioactive activity quantifies source strength. The International System of Units (SI) measures activity in Becquerels (Bq) or disintegrations per second (dps), whereas traditional CGS nuclear physics uses Curies (Ci), radiation counters use disintegrations per minute (dpm), and historical physics uses Rutherfords (Rd).
Our free online Radiation-Activity Converter provides instant, high-precision conversions across all SI, traditional CGS, nuclear medicine, and environmental decay rate units:
- Curies to Becquerels: Multiply Curies by
37,000,000,000(1 Ci = 3.7 × 1010 Bq = 37 GBq). - Becquerels to Curies: Multiply Becquerels by
2.7027027 × 10-11(1 GBq ≈ 0.027027 Ci = 27.027 mCi). - Millicuries to Megabecquerels: Multiply mCi by
37(1 mCi = 37 MBq; 10 mCi = 370 MBq). - Becquerels to Disintegrations per Second:
1 Bq = 1 dps = 1 s-1(exact 1:1 definition). - Disintegrations per Minute (dpm) to Becquerels: Divide dpm by
60(1 Bq = 60 dpm). - Rutherfords to Megabecquerels:
1 Rutherford (Rd) = 1,000,000 Bq = 1 MBq.
Master Radioactive Activity Unit Conversion Table
The table below displays exact relationships, SI power multipliers, and traditional health physics equivalents relative to 1 Becquerel (Bq):
| Radioactive Activity Unit | Symbol | Exact Value in Becquerels (Bq) | Equivalent in Curies (Ci) | System & Application Field |
|---|---|---|---|---|
| 1 Becquerel | Bq |
1.0 Bq (1 dps) |
2.702703 × 10-11 Ci | SI Base Derived Unit (1 decay/sec) |
| 1 Terabecquerel | TBq |
1.0 × 1012 Bq | 27.027027 Ci | Industrial Irradiator / Source Scale |
| 1 Gigabecquerel | GBq |
1.0 × 109 Bq | 0.027027 Ci (27.027 mCi) | Nuclear Medicine Therapy Scale |
| 1 Megabecquerel | MBq |
1.0 × 106 Bq | 2.7027 × 10-5 Ci (27.027 μCi) | Diagnostic Imaging Dose Scale |
| 1 Kilobecquerel | kBq |
1,000 Bq (103 Bq) | 2.7027 × 10-8 Ci (27.027 nCi) | Low-Level Calibration Source |
| 1 Millibecquerel | mBq |
0.001 Bq (10-3 Bq) | 2.7027 × 10-14 Ci | Environmental Water Tracer Scale |
| 1 Kilocurie | kCi |
3.7 × 1013 Bq (37 TBq) | 1,000 Ci |
Cobalt-60 Teletherapy Scale |
| 1 Curie | Ci |
37,000,000,000 Bq (37 GBq) |
1.0 Ci |
Traditional CGS Base Activity Unit |
| 1 Millicurie | mCi |
37,000,000 Bq (37 MBq) |
0.001 Ci | Radiopharmaceutical Patient Dose |
| 1 Microcurie | μCi |
37,000 Bq (37 kBq) |
0.000001 Ci | Smoke Detector Americium Source |
| 1 Nanocurie | nCi |
37.0 Bq |
1.0 × 10-9 Ci | Radiochemistry Assay Standard |
| 1 Picocurie | pCi |
0.037 Bq (2.22 dpm) |
1.0 × 10-12 Ci | EPA Radon Air Quality Unit |
| 1 Rutherford | Rd |
1,000,000 Bq (1 MBq) |
2.7027 × 10-5 Ci | Historical Nuclear Physics Unit |
| 1 Disintegration / Minute | dpm |
0.016667 Bq (1/60 Bq) | 4.504505 × 10-13 Ci | Scintillation Counter Reading |
Step-by-Step Calculation Example
To convert a standard 10 Millicurie (10 mCi) Fluorine-18 (FDG) PET scan dose into SI Megabecquerels (MBq):
10 mCi × 37 MBq/mCi = 370 Megabecquerels (370 MBq)
Thus, a 10 mCi radiopharmaceutical injection equals exactly 370 MBq (370,000,000 disintegrations per second).
Nuclear Medicine, Industry & Environmental Activity Benchmarks
Below is a comparative reference chart showing radioactive decay activity across everyday sources, medical diagnostics, and industrial radiopharmaceuticals:
| Radioactive Source / Application | Activity in SI Units (Bq / MBq / GBq) | Equivalent in Curies (μCi / mCi / Ci) | Nuclear & Radiochemistry Context |
|---|---|---|---|
| EPA Radon Air Action Limit (4 pCi/L) | 148 Bq/m³ (0.148 Bq/L) | 4.0 pCi/L (8.88 dpm/L) | Indoor home radon safety threshold |
| Human Body Natural Radioactivity (K-40) | 4,400 Bq (4.4 kBq) | ~0.12 μCi | Natural potassium-40 decay inside a 70 kg human body |
| Americium-241 Smoke Detector Source | 37,000 Bq (37 kBq) | 1.0 μCi | Alpha-particle ionization source in household detectors |
| PET Scan Fluorine-18 (FDG) Injection | 370 MBq (3.7 × 108 Bq) | 10.0 mCi | Standard diagnostic Positron Emission Tomography dose |
| Thyroid Cancer Iodine-131 Therapy Dose | 5.55 GBq (5.55 × 109 Bq) | 150.0 mCi | High-dose I-131 radiopharmaceutical ablation therapy |
| Industrial Radiography NDT Source | 3.7 TBq (3.7 × 1012 Bq) | 100.0 Ci | Iridium-192 / Cobalt-60 weld inspection camera |
History & Standards: Henri Becquerel vs. Marie & Pierre Curie vs. Rutherford
Henri Becquerel and the SI Unit (1975)
The SI unit of radioactive activity is named after French physicist Henri Becquerel (1852–1908), who discovered natural radioactivity in uranium salts in 1896 (sharing the 1903 Nobel Prize in Physics with Marie and Pierre Curie). In 1975, the 15th General Conference on Weights and Measures (CGPM) adopted the Becquerel (Bq) as the official SI unit for radioactivity, defined as 1 nuclear disintegration per second (1 Bq = 1 dps).
Marie & Pierre Curie and the Curie Unit (1910)
Introduced in 1910 at the Radiology Congress in Brussels in honor of Marie Curie and Pierre Curie, the Curie (Ci) was originally defined as the decay rate of 1.0 gram of pure Radium-226 in radioactive equilibrium with its daughter isotopes. In 1953, the International Commission on Radiation Units and Measurements (ICRU) standardized the Curie as exactly 37 billion disintegrations per second (1 Ci = 3.7 × 1010 Bq = 37 GBq).
Ernest Rutherford and the Rutherford Unit (1946)
In 1946, physicists E.U. Condon and L.F. Curtiss proposed the Rutherford (Rd) unit in honor of Ernest Rutherford (1871–1937), the father of nuclear physics who discovered alpha/beta radiation and atomic transmutation. Defined as exactly 1,000,000 disintegrations per second (106 dps = 1 MBq), the Rutherford served as a decimal alternative to the Curie before the adoption of the SI Becquerel.
To convert absorbed dose rates, visit our Radiation Converter. For radioisotope decay calculations over time, check our Half Life Calculator or explore our Conversion Calculator.
Frequently Asked Questions (FAQ)
How many Becquerels (Bq) are in 1 Curie (Ci)?
There are exactly 37,000,000,000 Becquerels (37 GBq or 3.7 × 1010 Bq) in 1 Curie (Ci).
How do I convert disintegrations per minute (dpm) to Becquerels (Bq)?
Since 1 Becquerel equals 1 disintegration per second, divide dpm by 60: Bq = dpm ÷ 60 (e.g., 120 dpm = 2 Bq).
What is the conversion between picocuries (pCi) and Becquerels (Bq) for radon gas?
1 picocurie (1 pCi) equals 0.037 Becquerels (Bq) (or 2.22 dpm). The US EPA indoor radon action level of 4 pCi/L corresponds to 148 Bq/m³.
Why is Fluorine-18 FDG PET scan dose measured in MBq or mCi?
Because radiopharmaceuticals decay rapidly in clinical applications. A typical patient injection of 10 mCi equals 370 MBq (370 million nuclear decays per second), providing sufficient gamma ray emission for 3D PET image reconstruction.