Radioactivity Converter — Bq, kBq, MBq, GBq, Ci, mCi, µCi
Convert any radioactivity value between SI (becquerel family) and traditional (curie family) units used in medicine, research, radiation protection and nuclear engineering.
From
To
- 1
Convert to the base unit
1 MBq × 1,000,000 = 1,000,000 - 2
Convert to the target unit
1,000,000 ÷ 37,000,000 = 0.027027 mCi
1 MBq =
| Becquerel | 1,000,000 Bq |
| Kilobecquerel | 1,000 kBq |
| Gigabecquerel | 0.001 GBq |
| Terabecquerel | 0.000001 TBq |
| Curie | 0.000027 Ci |
| Millicurie | 0.027027 mCi |
| Microcurie | 27.027027 µCi |
| Nanocurie | 27,027.027027 nCi |
Formula
How this is calculated
Radioactivity (also called activity) measures how many nuclear decays occur per second in a radioactive sample. The International System of Units defines the becquerel (Bq) as exactly one disintegration per second — a very small unit, so practical quantities are usually expressed in kBq (10³), MBq (10⁶), GBq (10⁹) or TBq (10¹²).
The older curie (Ci) was originally defined as the activity of one gram of pure ²²⁶Ra and is now fixed at exactly 3.7 × 10¹⁰ Bq. Medical nuclear imaging uses millicuries (mCi = 3.7 × 10⁷ Bq) and megabecquerels interchangeably — for example, a typical ⁹⁹ᵐTc bone scan uses about 700–800 MBq (≈ 20 mCi). The picocurie (pCi) is common in environmental radon measurements.
Conversion is a simple ratio through the base unit (becquerel): multiply by the source unit's "per-becquerel" factor, then divide by the target unit's factor. All factors here are exact by definition.
About this calculator
Radioactivity (activity) is the rate at which a radioactive material undergoes nuclear decay, measured in disintegrations per second. The SI unit, the becquerel (Bq), equals one decay per second. Because naturally occurring and artificial radioactive materials span many orders of magnitude — from a few decays per second in a smoke detector to 10¹⁸ Bq in a reactor fuel element — the unit system provides SI prefixes (kBq, MBq, GBq, TBq) for large activities.
The curie (Ci) pre-dates the becquerel and remains common in nuclear medicine and radiation safety in the United States. One curie equals exactly 3.7 × 10¹⁰ Bq (37 GBq), an amount close to the activity of 1 g of ²²⁶Ra. Submultiples — millicurie (mCi), microcurie (µCi), nanocurie (nCi) and picocurie (pCi) — are used for smaller sources. The rutherford (Rd = 10⁶ Bq = 1 MBq) is largely obsolete but appears in older texts.
Frequently asked questions
Exactly 3.7 × 10¹⁰ Bq (37 GBq). This is the defined value, not an approximation — the curie was redefined in 1975 to this exact figure to make it consistent with the SI.
Becquerel (Bq) measures the activity of a source — how many decays per second. Gray (Gy) measures absorbed dose — energy deposited per kilogram of tissue. Sievert (Sv) measures effective (biological) dose, weighting absorbed dose by radiation type and tissue sensitivity. They describe different aspects of radiation and are not interconvertible without additional information.
Indoor radon concentrations are typically very low — a few hundred becquerels per cubic metre of air, or equivalently a few picocuries per litre. The US EPA uses pCi/L as its standard radon reporting unit; 4 pCi/L (148 Bq/m³) is the action level recommended for remediation.
Also known as
TG we-Calculate Editorial Team. (2026). Radioactivity Converter — Bq, kBq, MBq, GBq, Ci, mCi, µCi [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/radiation-converter
TG we-Calculate Editorial Team. "Radioactivity Converter — Bq, kBq, MBq, GBq, Ci, mCi, µCi." TG we-Calculate. 2026. https://we-calculate.com/calculator/radiation-converter.
TG we-Calculate Editorial Team, "Radioactivity Converter — Bq, kBq, MBq, GBq, Ci, mCi, µCi," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/radiation-converter
@misc{wecalculate_radiation_converter, title = {Radioactivity Converter — Bq, kBq, MBq, GBq, Ci, mCi, µCi}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/radiation-converter}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?