Curie to Becquerel Conversion

Converts radioactivity measured in the traditional Curie unit to the SI unit Becquerel.

Written by the Vorzep Team

NuclearRadiationUnits

Curie to Becquerel Radioactivity Unit Converter

1 Ci = 3.7 × 10¹⁰ Bq · 1 mCi = 3.7 × 10⁷ Bq

Convert between Curies (Ci) and Becquerels (Bq). 1 Ci is exactly 3.7 × 10¹⁰ Bq.

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Curies (Ci)

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Becquerels (Bq)

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Radioactivity Conversion Reference 1 Ci = 3.7 × 10¹⁰ Bq

Parameter	Symbol	Value / Formula	Unit	Reference

1 Curie (Ci) = 3.7 × 10¹⁰ Becquerels (Bq) · Named after Marie and Pierre Curie · SI unit: Becquerel (1 decay per second)

A(Bq) = A(Ci) * 3.7 * 10^10

Curie to Becquerel Conversion

Variables

Symbol	Quantity	Unit
A(Bq)	Activity in Becquerels	Bq
A(Ci)	Activity in Curies	Ci

What it means

The becquerel (Bq) is the SI unit for activity (1 decay per second), while the curie (Ci) is a historical unit defined as the activity of 1 gram of radium‑226, which is 3.7×10¹⁰ Bq. This conversion factor is used in radiation protection, nuclear medicine, and regulatory compliance. Many older documents and regulations still use curies, so accurate conversion is important for safe handling and disposal. For example, a 1 mCi source = 37 MBq. Understanding this conversion helps professionals communicate activity values and adhere to legal limits. It also aids in comparing the activity of different isotopes and sources. Knowing the conversion is essential for radiation workers, regulators, and students of nuclear science.

Curie (Ci)	Equivalent Becquerels (Bq)	Scientific Notation
0.000000001 Ci (1 nCi)	37 Bq	3.7 × 10¹ Bq
0.000001 Ci (1 µCi)	37,000 Bq	3.7 × 10⁴ Bq
0.00001 Ci (10 µCi)	370,000 Bq	3.7 × 10⁵ Bq
0.0001 Ci (100 µCi)	3,700,000 Bq	3.7 × 10⁶ Bq
0.001 Ci (1 mCi)	37,000,000 Bq	3.7 × 10⁷ Bq
0.005 Ci (5 mCi)	185,000,000 Bq	1.85 × 10⁸ Bq
0.01 Ci (10 mCi)	370,000,000 Bq	3.7 × 10⁸ Bq
0.05 Ci (50 mCi)	1,850,000,000 Bq	1.85 × 10⁹ Bq
0.1 Ci	3,700,000,000 Bq	3.7 × 10⁹ Bq
0.25 Ci	9,250,000,000 Bq	9.25 × 10⁹ Bq
0.5 Ci	18,500,000,000 Bq	1.85 × 10¹⁰ Bq
1 Ci	37,000,000,000 Bq	3.7 × 10¹⁰ Bq
2 Ci	74,000,000,000 Bq	7.4 × 10¹⁰ Bq
5 Ci	185,000,000,000 Bq	1.85 × 10¹¹ Bq
10 Ci	370,000,000,000 Bq	3.7 × 10¹¹ Bq
25 Ci	925,000,000,000 Bq	9.25 × 10¹¹ Bq
50 Ci	1,850,000,000,000 Bq	1.85 × 10¹² Bq
100 Ci	3,700,000,000,000 Bq	3.7 × 10¹² Bq
500 Ci	18,500,000,000,000 Bq	1.85 × 10¹³ Bq
1,000 Ci	37,000,000,000,000 Bq	3.7 × 10¹³ Bq

Worked example

Curie to Becquerel Conversion – Two Examples

Real‑World

Scenario: A radiation source has an activity of 0.001 Ci (1 mCi). The health physicist converts this to becquerels to comply with SI unit regulations for reporting radiation source strength in a nuclear medicine facility.

Parameter	Value
Activity (Ci)	0.001

1A(Bq) = 0.001 × 3.7×10¹⁰ = 3.7×10⁷ Bq

Result 3.7×10⁷ Bq ✓ 37 MBq

Scenario: A radioactive source is rated at 10 Ci for industrial radiography. The radiation safety officer converts the activity to becquerels to prepare the transport documentation required by international regulations.

Parameter	Value
Activity (Ci)	10

1A(Bq) = 10 × 3.7×10¹⁰ = 3.7×10¹¹ Bq

Result 3.7×10¹¹ Bq ✓ 370 GBq

Nuclear insight: 1 Ci = 3.7×10¹⁰ Bq. The curie is the traditional unit (activity of 1 g of radium), while the becquerel is the SI unit.

Common mistakes

Conversion factor: 1 Ci = 3.7 × 10¹⁰ Bq exactly (definition).
Curie to Becquerel: Multiply Ci by 3.7×10¹⁰ to get Bq.
Becquerel to Curie: Divide Bq by 3.7×10¹⁰.
Historical: The curie is based on the activity of 1 gram of radium‑226.
SI unit: The becquerel is the SI unit – the curie is still used in some contexts.

Applications

The conversion between curies and becquerels, A(Bq) = A(Ci) × 3.7×10¹⁰, is a common unit conversion in nuclear science. The curie (Ci) is the traditional unit of activity, based on the activity of one gram of radium‑226, while the becquerel (Bq) is the SI unit. This conversion is used in international communication, regulatory compliance, and historical data interpretation. Radiation safety professionals, nuclear engineers, and medical physicists must be comfortable with both units to interpret regulations, compare data, and design equipment. By using the correct conversion factor, they ensure accurate reporting and adherence to safety standards across different jurisdictions and applications.

Conversion of activity values between SI and traditional units
Compliance with regulatory limits and reporting requirements
Historical data interpretation and legacy records
International collaboration in nuclear research and safety
Education and training in radiation measurement