Understanding Becquerels to Curies Conversion
The becquerel (Bq) is the SI unit of radioactivity, defined as one nuclear decay per second. The curie (Ci) is the older, much larger unit, originally based on the activity of one gram of radium-226 and now fixed at exactly 3.7 × 10¹⁰ decays per second. Converting from becquerels to curies is routine in health physics, nuclear medicine, and radiation safety, where legacy instruments, regulations, and source labels are often still expressed in curies.
Conversion Formula
To convert Becquerels to Curies, multiply by this factor:
Step-by-Step Example
Convert 25 Becquerels to Curies.
How to Convert Becquerels to Curies
Convert an SI activity in becquerels to the legacy curie in one step.
- Note the activity in Bq: Start with your value in becquerels.
- Multiply by 2.702703 × 10⁻¹¹: This scales becquerels to curies.
- Report in Ci: The product is the activity in curies.
- Worked result: For 25 Bq, 25 × 2.702703 × 10⁻¹¹ = 6.75676 × 10⁻¹⁰ Ci.
Becquerels to Curies conversion table
| Becquerels (Bq) | Curies (Ci) |
|---|---|
| 0 | 0 |
| 1 | 2.702703e-11 |
| 2 | 5.405405e-11 |
| 3 | 8.108108e-11 |
| 4 | 1.081081e-10 |
| 5 | 1.351351e-10 |
| 6 | 1.621622e-10 |
| 7 | 1.891892e-10 |
| 8 | 2.162162e-10 |
| 9 | 2.432432e-10 |
| 10 | 2.702703e-10 |
| 15 | 4.054054e-10 |
| 20 | 5.405405e-10 |
| 25 | 6.756757e-10 |
| 30 | 8.108108e-10 |
| 40 | 1.081081e-9 |
| 50 | 1.351351e-9 |
| 60 | 1.621622e-9 |
| 70 | 1.891892e-9 |
| 80 | 2.162162e-9 |
| 90 | 2.432432e-9 |
| 100 | 2.702703e-9 |
| 150 | 4.054054e-9 |
| 200 | 5.405405e-9 |
| 250 | 6.756757e-9 |
| 300 | 8.108108e-9 |
| 400 | 1.081081e-8 |
| 500 | 1.351351e-8 |
| 600 | 1.621622e-8 |
| 700 | 1.891892e-8 |
| 800 | 2.162162e-8 |
| 900 | 2.432432e-8 |
| 1000 | 2.702703e-8 |
| 2000 | 5.405405e-8 |
| 3000 | 8.108108e-8 |
| 4000 | 1.081081e-7 |
| 5000 | 1.351351e-7 |
| 10000 | 2.702703e-7 |
| 25000 | 6.756757e-7 |
| 50000 | 0.000001351351 |
| 100000 | 0.000002702703 |
| 250000 | 0.000006756757 |
| 500000 | 0.00001351351 |
| 1000000 | 0.00002702703 |
What is the Becquerel?
The becquerel is the SI derived unit of radioactivity, measuring the rate at which a quantity of radioactive material decays. It quantifies how many atomic nuclei disintegrate per second.
Definition
One becquerel is defined as one nuclear decay (disintegration) per second:
The becquerel has dimensions of inverse time (reciprocal seconds). It measures decay rate only, not the energy or biological effect of the emitted radiation, so it is distinct from dose units such as the gray or sievert.
Origin and History
The unit is named after French physicist Henri Becquerel, who discovered radioactivity in 1896 and shared the 1903 Nobel Prize in Physics with Marie and Pierre Curie. The becquerel was adopted by the General Conference on Weights and Measures in 1975, replacing the older curie for scientific use.
Law and Notable Facts
The becquerel is the coherent SI unit for activity and is recognized worldwide. Because a single becquerel is an extremely small rate, real-world quantities are usually expressed in kilobecquerels, megabecquerels, or gigabecquerels. One gram of radium-226 has an activity of about 37 gigabecquerels.
Real-World Examples and Conversions
- disintegration per second, roughly the trace activity in a few grams of ordinary soil.
- The human body naturally contains about 4000 to 5000 Bq of potassium-40 and carbon-14 activity.
- (curie) .
- Drinking-water limits are often set near a few Bq per litre for individual radionuclides.
What is the Curie?
The curie is a non-SI unit of radioactivity, historically defined by the activity of radium and still common in the United States and in the nuclear industry. It represents a very large decay rate compared with the SI becquerel.
Definition
One curie is defined as exactly nuclear decays per second:
That is, . The value was originally chosen to approximate the activity of one gram of radium-226, and was later fixed exactly at disintegrations per second.
Origin and History
The curie is named in honor of Marie and Pierre Curie, pioneers of radioactivity research. Defined in 1910 and refined at subsequent radiology congresses, it was tied to the activity of radium, the element the Curies isolated.
Law and Notable Facts
Although the SI unit of activity is the becquerel, the curie remains legally and commercially entrenched in the United States, where sealed sources, medical isotopes, and regulatory limits are frequently quoted in curies. One gram of radium-226 has an activity very close to one curie.
Real-World Examples and Conversions
- .
- .
- Industrial radiography and irradiator sources are often rated from tens to thousands of curies.
- One gram of radium-226 corresponds to approximately 1 curie of activity.
Frequently Asked Questions
How many curies are in one becquerel?
One becquerel equals about 2.702703 × 10⁻¹¹ curies, because the curie is an enormous unit of activity by comparison.
What is the reverse conversion?
Multiply curies by 3.7 × 10¹⁰ (37,000,000,000) to obtain becquerels.
Why is the curie so much larger than the becquerel?
The curie was defined from the activity of one gram of radium-226, which undergoes about 37 billion decays per second, whereas one becquerel is just a single decay per second.
Where is the becquerel-to-curie conversion used?
It is common in nuclear medicine, radiation protection, and regulatory reporting, where sources and limits may be specified in curies even though measurements are made in becquerels.
Which unit is the SI standard?
The becquerel is the official SI unit of activity; the curie is a legacy unit that remains in wide practical and regulatory use.
People also convert
Complete Becquerels conversion table
| Unit | Result |
|---|---|
| Kilobecquerels (kBq) | 0.001 kBq |
| Megabecquerels (MBq) | 0.000001 MBq |
| Curies (Ci) | 2.702703e-11 Ci |
| Millicuries (mCi) | 2.702703e-8 mCi |
| Microcuries (uCi) | 0.00002702703 uCi |