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Radioactivity Converter

Converter

Activity Conversion

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Example Conversions

Activity

1 Ci = 3.70e+10 Bq

Absorbed Dose

1 Gy = 100.00 rad

Equivalent Dose

500 mSv = 50.00 rem

Exposure

1 R = 2.58e-4 C/kg

About This Tool

Radioactivity Converter – Activity, Absorbed Dose, Equivalent Dose, and Exposure

The Radioactivity Converter is a free online tool for converting between all major units of nuclear radiation measurement. It covers four independent categories — Activity, Absorbed Dose, Equivalent Dose, and Exposure — supporting the complete range of units used in nuclear medicine, radiation protection, health physics, experimental physics, and environmental monitoring. All calculations are performed client-side with no data sent to any server.

Whether you need to convert Curie to Becquerel for a radiopharmaceutical dose, Gray to Rad for a legacy dosimetry report, Millisievert to Rem for US regulatory compliance, or Roentgen to C/kg for an SI-equivalent exposure value, this tool gives you the answer instantly along with a full multi-unit comparison table.

The Four Conversion Categories

Activity (Becquerel, Curie, and more)

Activity measures the rate of radioactive decay of a source — how many nuclear disintegrations occur per unit time. The SI unit is the Becquerel (Bq), defined as one disintegration per second. The traditional unit, the Curie (Ci), was originally defined as the activity of one gram of radium-226 and equals exactly 3.7 × 10¹⁰ Bq. Supported units include Bq, kBq, MBq, GBq, TBq, Ci, mCi, µCi, nCi, pCi, disintegrations per minute (dpm), and the historical Rutherford (Rd).

Common activity examples: a typical PET scan uses ~370 MBq of FDG; the US EPA action level for indoor radon is 4 pCi/L; a smoke detector contains roughly 1 µCi of americium-241.

Absorbed Dose (Gray and Rad)

Absorbed dose measures the energy deposited per unit mass of matter by ionising radiation, regardless of radiation type. The SI unit is the Gray (Gy), equal to 1 joule per kilogram. The traditional unit, the Rad, equals exactly 0.01 Gy. Supported units include Gy, mGy, µGy, kGy, rad, and mrad. The kilogray (kGy) is common in industrial radiation processing such as food sterilization and polymer cross-linking.

Equivalent Dose (Sievert and Rem)

Equivalent dose weights the absorbed dose by the biological effectiveness of the radiation type, expressed using a radiation weighting factor (wR). For X-rays and gamma rays wR = 1, so 1 Gy = 1 Sv; for alpha particles wR = 20. The SI unit is the Sievert (Sv); the traditional unit is the Rem, equal to exactly 0.01 Sv. Supported units include Sv, mSv, µSv, rem, and mrem. The global average annual background dose is approximately 2.4 mSv.

Exposure (Coulomb/kg and Roentgen)

Exposure quantifies the ionisation produced in dry air by X-ray or gamma radiation only — it does not apply to neutrons, alpha, or beta radiation. The SI unit is the Coulomb per kilogram (C/kg). The traditional unit, the Roentgen (R), equals exactly 2.58 × 10⁻⁴ C/kg. Supported units include C/kg, mC/kg, R, and mR.

Cross-category conversion
Converting between categories — for example, from Becquerel to Gray — requires knowledge of the specific radionuclide, target tissue, geometry, and radiation weighting factor. These are dosimetry calculations, not simple unit conversions, and are outside the scope of this tool.

How Radioactivity Unit Conversion Works

Within each category the converter normalizes through an SI base unit in two steps. First, the input value is multiplied by the source unit's conversion factor to obtain the equivalent in the base unit. Then the base-unit value is divided by the target unit's conversion factor to produce the final result.

Example — converting 1 Ci to Bq:

  • 1 Ci × 3.7 × 10¹⁰ Bq/Ci = 3.7 × 10¹⁰ Bq

Example — converting 500 mSv to rem:

  • 500 mSv × 0.001 Sv/mSv = 0.5 Sv
  • 0.5 Sv ÷ 0.01 Sv/rem = 50 rem

Radiation Dose Reference Values

  • Annual background dose (global average): ~2.4 mSv
  • Chest X-ray: ~0.1 mSv
  • Chest CT scan: ~5–10 mSv
  • Occupational dose limit (ICRP): 20 mSv/year
  • Radiation sickness threshold (acute): ~1,000 mSv (1 Sv)
  • US EPA radon action level: 4 pCi/L
  • Typical PET scan administered activity: 185–370 MBq

Practical Applications

  • Nuclear medicine: Radiopharmaceutical doses are typically specified in MBq or mCi. Converting between these units is essential when comparing protocols that use different unit conventions.
  • Radiation protection: Occupational dose limits and public dose constraints are expressed in Sv or rem depending on jurisdiction. The US NRC uses rem and mrem; international standards (ICRP, IAEA) use Sv and mSv.
  • Environmental monitoring: Radon measurement in buildings is commonly expressed in pCi/L in the United States and Bq/m³ in Europe. Converting between these helps compare international guidelines.
  • Industrial radiography: Source activities and exposure levels in industrial non-destructive testing are often specified in Ci or R/hr, while modern calibration requires SI equivalents.
  • Physics and research: Historical literature and equipment manuals may use Curie, Rad, Rem, or Roentgen. This tool provides quick conversion to modern SI equivalents for accurate comparison.
This tool is for unit conversion only
Radioactivity measurements and dose calculations must be interpreted by qualified radiation safety professionals. The reference values provided are for educational context only and do not constitute medical, safety, or regulatory advice.

Tips for Using the Converter

  • Select the correct category tab first — Activity, Absorbed Dose, Equivalent Dose, or Exposure — before choosing units. Units in different categories cannot be mixed.
  • For values in scientific notation (common in nuclear physics), enter them as standard decimals or use the full value. For example, enter 37000000000 instead of 3.7e10.
  • Enable Show all unit conversions to display the input value expressed in every supported unit simultaneously — useful for cross-referencing readings from different instruments.
  • Use the Swap button to reverse the conversion direction and verify round-trip accuracy.
  • Increase decimal places to 8–10 for high-precision work, or reduce to 2–3 for quick estimates. The tool automatically switches to scientific notation for very large or very small results.

Frequently Asked Questions

Is the Radioactivity Converter free?

Yes, Radioactivity Converter is totally free :)

Can I use the Radioactivity Converter offline?

Yes, you can install the webapp as PWA.

Is it safe to use Radioactivity Converter?

Yes, any data related to Radioactivity Converter only stored in your browser (if storage required). You can simply clear browser cache to clear all the stored data. We do not store any data on server.

How does this radioactivity converter work?

The tool converts values within four independent categories: Activity, Absorbed Dose, Equivalent Dose, and Exposure. Within each category, every conversion normalizes through an SI base unit — Becquerel (Bq) for activity, Gray (Gy) for absorbed dose, Sievert (Sv) for equivalent dose, and Coulomb per kilogram (C/kg) for exposure. The input is multiplied by the source unit's conversion factor to reach the base unit, then divided by the target unit's conversion factor to produce the final result.

What is the difference between Activity, Absorbed Dose, Equivalent Dose, and Exposure?

Activity (Bq or Ci) measures how many radioactive disintegrations occur per second in a source. Absorbed Dose (Gy or rad) measures the energy deposited per kilogram of matter by ionising radiation. Equivalent Dose (Sv or rem) weights the absorbed dose by the biological effectiveness of each radiation type to express health risk. Exposure (C/kg or Roentgen) quantifies the ionisation produced specifically in air by X-ray or gamma radiation and is not applicable to other radiation types or materials.

Why can't I convert between categories — for example, from Becquerel to Gray?

Cross-category conversions are intentionally not supported because they require additional information. Converting from activity to dose requires knowing the specific radionuclide, the target tissue, geometry, and shielding conditions — none of which are single conversion factors. Converting from absorbed dose to equivalent dose requires the radiation weighting factor (wR), which varies by radiation type (e.g., 1 for gamma, 20 for alpha particles). These calculations are beyond the scope of a unit converter.

What is the difference between the Sievert and the Gray?

The Gray (Gy) measures the physical energy absorbed per kilogram of any material — it is radiation-type-agnostic. The Sievert (Sv) is the Gray multiplied by a radiation weighting factor (wR) that accounts for the relative biological damage caused by different types of radiation. For X-rays and gamma rays, wR = 1, so 1 Gy = 1 Sv. For alpha particles, wR = 20, so 1 Gy of alpha radiation equals 20 Sv of equivalent dose.

What radiation doses are considered safe or dangerous?

The global average annual background radiation dose is approximately 2.4 mSv. Occupational dose limits are typically 20 mSv per year (ICRP recommendation) or 50 mSv per year (US NRC limit). Acute whole-body doses above ~1 Sv can cause radiation sickness; doses above ~4 Sv without medical treatment have a 50% fatality rate (LD50). Diagnostic X-rays deliver doses well below 50 mSv. This tool is designed for unit conversion only and does not constitute medical or radiation safety advice.

Are my conversion results accurate for scientific and regulatory use?

Yes. All conversion factors are based on exact SI definitions and internationally recognised relationships: 1 Ci = 3.7 × 10¹⁰ Bq (exact, by historical definition), 1 rad = 0.01 Gy (exact), 1 rem = 0.01 Sv (exact), 1 R = 2.58 × 10⁻⁴ C/kg (exact). Calculations use IEEE 754 double-precision floating-point arithmetic (approximately 15 significant digits). For regulatory submissions, always verify against the applicable standards of your jurisdiction.