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Radioactivity Converter

Science

Convert radioactivity units instantly — becquerel, curie, millicurie, microcurie, and gigabecquerel. Used in nuclear medicine, radiation safety, and physics.

Reviewed by the thecalcu.com team · Last updated June 29, 2026

From
To
All conversionsfor 1 Becquerel (Bq)
Becquerel (Bq)1
Kilobecquerel (kBq)0.001
Megabecquerel (MBq)0.000001
Gigabecquerel (GBq)1.0000e-9
Terabecquerel (TBq)1.0000e-12
Curie (Ci)2.7027e-11
Millicurie (mCi)2.7027e-8
Microcurie (µCi)0.000027027027
Nanocurie (nCi)0.027027027
Picocurie (pCi)27.027027
Rutherford (Rd)0.000001
Disintegrations/second1
Disintegrations/minute59.999999

What is a Radioactivity?

A Radioactivity Converter translates between units of radioactive activity, the rate at which a radioactive material undergoes nuclear disintegrations. The SI unit is the becquerel (Bq), defined as one disintegration per second. The legacy unit is the curie (Ci), which equals 3.7 × 10¹⁰ Bq and was historically defined as the activity of one gram of radium-226.

Because the curie is an enormous unit relative to everyday radioactive sources, subunits are routinely used: millicurie (mCi, 10⁻³ Ci = 3.7 × 10⁷ Bq), microcurie (µCi, 10⁻⁶ Ci = 37,000 Bq), nanocurie (nCi, 10⁻⁹ Ci = 37 Bq). Similarly, becquerel subunits scale up for medical and industrial applications: kilobecquerel (kBq), megabecquerel (MBq), gigabecquerel (GBq), and terabecquerel (TBq).

The converter covers 13 units:

  • SI: Bq, kBq, MBq, GBq, TBq
  • Legacy: Ci, mCi, µCi, nCi, pCi, Rd (rutherford)
  • Direct count: dps (= Bq), dpm

Nuclear medicine in India uses MBq and mCi interchangeably. For context: a standard chest X-ray exposes the patient to roughly the same effective dose as 10 hours of background radiation, while a nuclear medicine thyroid scan uses 74–400 MBq of Tc-99m.

Why Use a Radioactivity Converter?

Nuclear medicine protocols in India may specify doses in mCi (older US-origin protocols) or MBq (modern SI protocols). Radiation safety regulations mix Bq (SI) and Ci (legacy) depending on the regulating body and the age of the standard. Equipment from different manufacturers reports activity in different units. The converter eliminates look-up errors in these cross-unit scenarios.

Who Should Use This Converter?

Nuclear medicine physicians and technologists, converting between MBq and mCi for dose preparation and prescription.

Radiation safety officers, checking activity limits across regulations that use both SI and legacy units.

Biochemistry researchers, working with radiotracer experiments where scintillation counters report in dpm and protocols specify in µCi.

Physics students, understanding the historical transition from curie to becquerel and the scale of nuclear processes.

What Does the Radioactivity Converter Give You?

A single activity value converted between all 13 units simultaneously. The reference table is particularly useful for comparing nuclear medicine dose protocols across institutions using different unit conventions.

How to use this Radioactivity calculator

  1. Enter the radioactivity value in the From field.
  2. Select the From unit (e.g. MBq).
  3. Select the To unit (e.g. mCi).
  4. The converted value appears instantly.
  5. Use the reference table to see all equivalent values at once.
  6. Click ⇄ to reverse the conversion.

Formula & Methodology

Base unit: Becquerel (Bq) = 1 disintegration per second

| Unit | Bq equivalent |
|---|---|
| Bq | 1 |
| kBq | 1,000 |
| MBq | 1,000,000 |
| GBq | 1,000,000,000 |
| TBq | 1,000,000,000,000 |
| Ci | 37,000,000,000 (= 3.7 × 10¹⁰) |
| mCi | 37,000,000 |
| µCi | 37,000 |
| nCi | 37 |
| pCi | 0.037 |
| Rd | 1,000,000 |
| dps | 1 (identical to Bq) |
| dpm | 1/60 ≈ 0.01667 |

Worked example: Convert 200 MBq (typical PET dose) to mCi.
- 200 × 10⁶ Bq ÷ 37 × 10⁶ Bq/mCi = 5.41 mCi

Common medical activity reference:
| Procedure | Typical activity |
|---|---|
| ¹⁸F-FDG PET/CT | 200–400 MBq (5–11 mCi) |
| ⁹⁹ᵐTc bone scan | 740 MBq (20 mCi) |
| ¹³¹I thyroid ablation | 1,110–5,550 MBq (30–150 mCi) |
| ¹²³I thyroid scan | 74–185 MBq (2–5 mCi) |

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Frequently Asked Questions

Radioactivity is the spontaneous disintegration of unstable atomic nuclei, releasing radiation in the form of alpha particles, beta particles, or gamma rays. Activity, the rate of these disintegrations, is the primary measurement of radioactivity. The SI unit is the becquerel (Bq), defined as one disintegration per second. The older unit, the curie (Ci), was defined as the activity of 1 gram of radium-226 and equals 3.7 × 10¹⁰ Bq.
1 curie (Ci) = 37,000,000,000 Bq (3.7 × 10¹⁰ Bq). This is a very large number, the becquerel is a very small unit (one disintegration per second), while the curie was chosen to represent the activity of radium, which is intensely radioactive. In nuclear medicine, millicurie (mCi) and microcurie (µCi) are common because medical doses involve much smaller activities.
Nuclear medicine departments in India use both megabecquerel (MBq) and millicurie (mCi) depending on the procedure and the age of the equipment/protocols. The standard PET/CT dose of F-18 FDG is typically 200–400 MBq (5–10 mCi). Technetium-99m doses for SPECT imaging are in the range of 200–1,000 MBq. Modern protocols increasingly use MBq exclusively.
A megabecquerel (MBq) is one million becquerels (10⁶ Bq). It is the standard unit for nuclear medicine doses, equivalent to approximately 0.027 mCi. Common isotope doses: ⁹⁹ᵐTc bone scan ≈ 740 MBq (20 mCi), ¹³¹I thyroid ablation ≈ 3,700–5,550 MBq (100–150 mCi), ¹⁸F-FDG PET ≈ 200–400 MBq (5–11 mCi).
Background radiation from natural sources (cosmic rays, radon, soil, food) delivers approximately 2–3 mSv of effective dose per year to an average person in India, corresponding to an extremely low but non-zero activity from distributed sources. The activity in the human body from natural potassium-40 alone is approximately 4,000 Bq, about 4 kBq.
Activity (Bq or Ci) measures the rate of radioactive disintegrations, how often a source emits radiation. Dose (sievert, Sv, or rem) measures the energy deposited in tissue and the biological effect. Activity alone does not determine dose, it also depends on the type of radiation, energy, and how close the source is to the body. A 1 MBq source of alpha emitters is far more hazardous internally than 1 MBq of gamma emitters.
The curie (Ci) was defined in 1910 as the activity of one gram of radium-226, which happens to be 3.7 × 10¹⁰ disintegrations per second. It was the dominant unit in nuclear physics and medicine before SI units were adopted. Despite the official preference for becquerel, curie and its subunits (mCi, µCi, nCi) remain widely used in the US and in older nuclear medicine protocols worldwide.
A rutherford (Rd), named after Ernest Rutherford, is a historical unit equal to 10⁶ disintegrations per second (= 1 MBq). It was proposed as an intermediate unit between the very large curie and the very small becquerel, but it was never adopted as an SI unit and is now rarely encountered outside historical literature.
Disintegrations per minute (dpm) is a direct count of nuclear disintegrations per minute, equal to 1/60 Bq or approximately 0.01667 Bq. It is used in scintillation counting and radiotracer experiments in biology and biochemistry, where liquid scintillation counters report results in dpm or counts per minute (cpm). 1 µCi = 2.22 × 10⁶ dpm.
Radioactive isotopes are used diagnostically (PET scans, SPECT imaging) and therapeutically (radioiodine for thyroid cancer, Y-90 microspheres for liver tumours, Lu-177 for neuroendocrine tumours). India has a growing nuclear medicine infrastructure with PET/CT centres in major hospitals. The Bhabha Atomic Research Centre (BARC) produces several medical isotopes domestically.
Food safety regulators set activity limits per kilogram of food for specific isotopes. The FSSAI (India) and Codex Alimentarius specify activity concentrations for radionuclides in Bq/kg or Bq/L. For drinking water, WHO guidance for Cs-137 is 10 Bq/L. These concentration-based limits are different from the total activity limits used in medical and industrial contexts.
Also known as
becquerel to curieBq to Ci converterradioactivity unit converternuclear activity convertermillicurie to megabecquerelcurie to becquerelradiation unit converteractivity unit converter