What is 1 curie in becquerels?

1 curie (Ci) equals exactly 3.7 × 10^10 becquerels (37,000,000,000 Bq or 37 GBq). This factor was defined in 1910 based on the decay rate of 1 gram of radium-226.

What does a becquerel measure?

One becquerel (Bq) equals one radioactive disintegration per second. It is the SI unit of radioactivity, adopted by the IUPAC and used in scientific and medical contexts worldwide.

The curie (Ci) is a traditional (non-SI) unit of radioactivity named after Marie and Pierre Curie. It was originally defined as the decay rate of 1 gram of radium-226, which equals 3.7 × 10^10 disintegrations per second.

How do I convert millicuries to megabecquerels?

1 mCi = 0.001 Ci = 3.7 × 10^7 Bq = 37 MBq. Multiply mCi by 37 to get MBq. This conversion is common in nuclear medicine where doses are often listed in both units.

Is the curie still used today?

Yes, particularly in the United States. Nuclear medicine, industrial radiography, and some regulatory documents still quote activities in Ci or mCi. Most international scientific literature uses Bq, MBq, or GBq.

How accurate is this converter?

The conversion factor 1 Ci = 3.7 × 10^10 Bq is exact by definition (BIPM). This tool uses full 64-bit floating-point precision throughout; rounding only applies to the display.

Curies to Becquerels Converter

Enter a value in curies (Ci, mCi, or µCi) and instantly see the equivalent in becquerels, kilobecquerels, megabecquerels, or gigabecquerels.

Enter Radioactivity

Input unit

Value

Exact factor: 1 Ci = 3.7 × 10¹⁰ Bq | 1 mCi = 3.7 × 10⁷ Bq | 1 µCi = 3.7 × 10⁴ Bq

Result

Becquerels (Bq)

—

Base SI unit

Kilobecquerels (kBq)

—

× 10³ Bq

Megabecquerels (MBq)

—

× 10⁶ Bq

Gigabecquerels (GBq)

—

× 10⁹ Bq

Quick Reference Table

Curies (Ci)	Becquerels (Bq)	MBq	Common context
1 µCi	37,000	0.037	Small lab tracer dose
1 mCi	37,000,000	37	Typical nuclear medicine diagnostic dose
10 mCi	370,000,000	370	Thyroid scan activity
1 Ci	37,000,000,000	37,000	Industrial sealed source
1,000 Ci	3.7 × 10¹³	3.7 × 10⁷	Large irradiator / spent fuel

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Summary

This converter translates radioactivity measurements from the traditional curie (Ci) into the SI unit becquerel (Bq) using the exact conversion factor 1 Ci = 3.7 × 10^10 Bq (37 billion disintegrations per second). It accepts full curies, millicuries, and microcuries, and displays the result alongside scaled SI prefixes (kBq, MBq, GBq) for readability. All computation runs in your browser with no server calls.

How it works

Select your input unit: Ci (curie), mCi (millicurie), or µCi (microcurie).
Enter the radioactivity value in the input field.
The converter multiplies by the appropriate factor to get becquerels.
Results are shown in Bq, kBq, MBq, and GBq simultaneously.
Copy any result with one click.

Use cases

Convert legacy nuclear medicine doses from mCi to MBq for modern reporting.
Translate Ci-based laboratory source activities into SI units for documentation.
Cross-check radioactive waste classifications that mix Ci and Bq values.
Convert radiation safety limits between traditional and SI unit systems.
Verify instrument calibration specifications listed in different unit systems.
Prepare patient records that require both Ci and Bq values.

Frequently Asked Questions

Last updated: 2026-07-14 · Reviewed by Nham Vu