☢️ Radioactivity Conversion Calculator 2026
Convert between becquerel, curie, rutherford, and all SI prefixes
1 Ci = 3.7 × 10¹⁰ Bq
Formula: value × 3.7 × 10¹⁰
📊 All Conversions
⚠️ Safety Notice: This calculator is for unit conversion only. For radiation safety, dose
calculations, or health physics, consult qualified professionals and use proper measurement equipment.
Common Radioactivity Conversions
| From | To | Multiply by |
|---|---|---|
| 1 curie (Ci) | becquerel (Bq) | 3.7 × 10¹⁰ |
| 1 becquerel (Bq) | curie (Ci) | 2.7 × 10⁻¹¹ |
| 1 millicurie (mCi) | megabecquerel (MBq) | 37 |
| 1 microcurie (µCi) | kilobecquerel (kBq) | 37 |
| 1 rutherford (Rd) | becquerel (Bq) | 10⁶ |
Understanding Radioactivity Units
⚛️ Becquerel (Bq)
SI unit. 1 Bq = 1 decay per second. Named after Henri Becquerel. Modern standard unit. Very small — typical samples are kBq to GBq.
☢️ Curie (Ci)
Legacy unit. 1 Ci = 3.7 × 10¹⁰ Bq. Original activity of 1 gram of Ra-226. Very large — medical uses typically mCi or µCi.
🔬 Rutherford (Rd)
Obsolete unit. 1 Rd = 10⁶ Bq = 1 MBq. Named after Ernest Rutherford. Rarely used today; replaced by MBq.
📐 Activity vs Dose
Activity (Bq) = decays/second. Dose (Sv, Gy) = energy absorbed. Different isotopes with same activity can have very different dose/harm.
Typical Activity Levels
| Source | Activity |
|---|---|
| Human body (K-40, C-14) | ~7,000 Bq |
| Smoke detector (Am-241) | ~30 kBq (0.9 µCi) |
| Medical thyroid scan (I-131) | ~150 MBq (4 mCi) |
| PET scan (F-18) | ~400 MBq (11 mCi) |
| Industrial radiography source | 1-5 TBq (30-140 Ci) |
| 1 gram Radium-226 | 37 GBq (1 Ci) — by definition |
Frequently Asked Questions
What is radioactivity?
Radioactivity is the spontaneous emission of particles or energy
from unstable atomic nuclei. Measured as decays per unit time. Unit: becquerel (Bq) or curie (Ci).
How do I convert curie to becquerel?
Multiply by 3.7 × 10¹⁰. 1 Ci = 37,000,000,000 Bq = 37 GBq. This is
the activity of 1 gram of radium-226.
How do I convert becquerel to curie?
Divide by 3.7 × 10¹⁰ or multiply by 2.7 × 10⁻¹¹. Example: 1 GBq =
0.027 Ci = 27 mCi.
What is a becquerel?
SI unit of radioactivity. 1 Bq = 1 radioactive decay per second.
Named after Henri Becquerel who discovered radioactivity in 1896.
What is a curie?
Historical unit. 1 Ci = 3.7 × 10¹⁰ Bq. Defined as the activity of
1 gram of Ra-226. Named after Marie and Pierre Curie. Still used in US medical/industrial contexts.
Why is 1 Ci = 3.7 × 10¹⁰ Bq?
The curie was defined as the disintegration rate of 1 gram of
radium-226. This happens to be approximately 3.7 × 10¹⁰ decays/second.
What is a rutherford?
Obsolete unit. 1 Rd = 10⁶ Bq = 1 MBq. Named after Ernest
Rutherford. Was used briefly but replaced by megabecquerel (MBq).
What is the difference between activity and dose?
Activity (Bq) = number of decays/second. Dose
(Sv, Gy) = energy absorbed by tissue. Same activity can produce different doses depending on radiation
type and energy.
What activity is dangerous?
Depends on isotope, type, exposure. 1 MBq of I-131 (thyroid) is
more concerning than 1 MBq of Tc-99m (short half-life). Consult health physics experts for safety
assessment.
How is radioactivity measured?
Detectors: Geiger-Müller counters, scintillation detectors,
semiconductor detectors. They count decay events and calibrate to Bq or Ci.
What is specific activity?
Activity per unit mass (Bq/g or Ci/g). Pure radioisotopes have
high specific activity. Natural uranium: ~25 kBq/g. Pure I-131: ~4.6 PBq/g.
How much radioactivity is in the human body?
~7,000 Bq mainly from K-40 and C-14. About 4,400 Bq from K-40,
rest from C-14 and traces of other isotopes. Natural and unavoidable.
What activity is in a smoke detector?
~30 kBq (0.9 µCi) of Am-241. Alpha emitter with 432-year
half-life. Safe when sealed; ionizes air to detect smoke particles.
What is half-life?
Time for half the atoms to decay. Activity halves each half-life.
C-14: 5,730 years. I-131: 8 days. Tc-99m: 6 hours. Doesn't change with activity units.
Why use Bq instead of Ci?
Bq is SI standard, used internationally. Easier to relate to other
SI units. Ci is convenient for larger sources but arbitrary (based on radium). Medicine transitioning to
Bq.
What prefixes are common for Bq?
kBq (10³): environmental. MBq (10⁶): medical
diagnostics. GBq (10⁹): therapy. TBq (10¹²): industrial sources.
How accurate is this radioactivity converter?
Uses exact conversion: 1 Ci = 3.7 × 10¹⁰ Bq. All SI prefixes use
exact powers of 10. Results are mathematically precise.