Radiation Converter
Convert becquerel, curie, gray, rad, sievert, rem and roentgen — with the four radiation quantities held strictly apart, because becquerels can never be turned into sieverts.
Radiation Converter
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What this result does not account for
- Activity cannot be converted to dose here, or anywhere, without a full isotope-specific dosimetric assessment.
- Exposure to absorbed dose is refused because the f-factor varies with photon energy and absorbing material.
- Neutron weighting is a continuous function of energy; the discrete values offered here are representative bands, not the ICRP curve.
In short: Radiation units describe four separate quantities. Activity (becquerel, curie) counts decays per second. Absorbed dose (gray, rad) is energy deposited per kilogram. Equivalent dose (sievert, rem) weights that energy by biological harm. Exposure (roentgen) measures ionisation in air. Converting within each is exact — 1 Ci = 37 GBq, 1 Gy = 100 rad, 1 Sv = 100 rem — but no factor converts activity into dose.
Formula
Conversions run within each quantity by an exact factor. Absorbed dose reaches equivalent dose through the radiation weighting factor wᴿ. Activity and exposure have no fixed bridge to dose at all.
Worked Example
- Identify the quantity. Millisievert is equivalent dose.
- Convert to the SI base. 1 mSv × 0.001 = 0.001 Sv.
- Divide by the target factor. One millirem is 10−5 Sv, so 0.001 ÷ 10−5 = 100 mrem.
- To reach sieverts from grays, name the radiation. H = wᴿD, so 1 Gy of alpha is 20 Sv while 1 Gy of gamma is 1 Sv.
- Do not attempt becquerels to sieverts. No factor exists; it requires a full dosimetric assessment.
Why one gray is not always one sievert. For gamma rays, X-rays, beta particles and electrons the radiation weighting factor is exactly 1, so a gray of absorbed dose is a sievert of equivalent dose and the two units appear interchangeable. They are not. Alpha particles deposit their energy over a very short track, causing dense clusters of damage, and carry a weighting factor of 20: one gray of alpha is twenty sieverts, or two thousand rem. Neutrons run from 5 to 20 depending on energy. The gray measures physics and the sievert estimates biology, and the two only coincide for the most common case.
Strengths & Limits Of This Model
Where this engine is strong
- Holds activity, absorbed dose, equivalent dose and exposure strictly apart instead of merging them into one dropdown.
- Applies ICRP radiation weighting factors explicitly and states that the result is weighted rather than converted.
- Refuses becquerel to sievert with an explanation rather than inventing a factor.
Where it stops
- Not a dosimetry or radiation-protection assessment tool.
- Does not model shielding, distance or decay over time.
- Perspective bands are population averages, not individual risk estimates.
Practical Use Cases
Reading a dosimeter or survey meter
Personal dosimeters report in millisieverts or millirem while older survey meters read in milliroentgen per hour, and the three are not the same quantity.
Nuclear medicine and radiopharmacy
Injected activity is prescribed in megabecquerels or millicuries; the resulting patient dose in millisieverts comes from published isotope specific coefficients, never from a unit conversion.
Regulatory reporting across jurisdictions
SI documents use becquerel, gray and sievert while much US material remains in curie, rad and rem, so cross-reading requires exact factors.
Radiation safety training
Explaining why activity does not equal dose is the single most useful thing a converter can do — pair with the Energy Converter when working from joules per kilogram.
Methodology & Editorial Standards
This converter treats the four radiological quantities separately, as ICRP and the SI both require. Activity routes through the becquerel, with the curie fixed at exactly 3.7 × 10¹⁰ Bq and the rutherford at 10⁶ Bq. Absorbed dose routes through the gray, with the rad at exactly 0.01 Gy. Equivalent dose routes through the sievert, with the rem at exactly 0.01 Sv. Exposure routes through the coulomb per kilogram, with the roentgen at exactly 2.58 × 10⁻⁴ C/kg. The only crossing permitted is absorbed dose to equivalent dose, computed as H = wᴿD using ICRP Publication 103 radiation weighting factors: 1 for photons and electrons, 2 for protons, 20 for alpha particles and fission fragments, and 5 to 20 for neutrons according to energy. Activity to dose is refused because it depends on the isotope, emission spectrum, geometry, shielding, exposure duration and, for internal exposure, biokinetics. Exposure to dose is refused because the f-factor varies with photon energy and absorbing material. Perspective figures cite UNSCEAR global average background of approximately 2.4 mSv per year. All conversion factors are exact by definition under the International System of Units, or exact by international agreement where the unit is defined by treaty. Values are held at full IEEE-754 double precision internally and rounded only for display, so chained conversions do not accumulate drift.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Radiation Converter — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How do I convert becquerels to sieverts?
You cannot, and any tool that offers to is fabricating the answer. A becquerel counts one decay per second in a source; a sievert measures biologically weighted energy absorbed by a person. The link between them depends on which isotope, what it emits, how far away you are, what shielding is present, how long you are there and whether the material is inside you. Radiation protection bodies publish dose coefficients per isotope and per pathway for exactly this reason.
How many becquerels are in a curie?
Exactly 37 billion, or 3.7 × 10¹⁰ Bq. The curie was originally defined as the activity of one gram of radium-226 and was later fixed at that round figure. It is a very large unit, so practical work uses millicuries and microcuries, or in SI, megabecquerels and gigabecquerels. One millicurie is 37 MBq.
What is the difference between a gray and a sievert?
A gray is pure physics: one joule of energy deposited per kilogram of material. A sievert is that same energy multiplied by a weighting factor reflecting how damaging the particular radiation is to tissue. For gamma, X-rays and beta the factor is 1 and the numbers match. For alpha it is 20, so one gray becomes twenty sieverts. Grays describe what happened; sieverts estimate what it means.
Is 1 sievert the same as 100 rem?
Yes, exactly. The rem is the legacy unit of equivalent dose and is defined as one hundredth of a sievert, so 1 mSv is 100 mrem and 1 µSv is 0.1 mrem. The same relationship holds between the gray and the rad for absorbed dose. US regulations and older instruments still work in rem, so the conversion comes up constantly.
How much radiation is dangerous?
Natural background averages about 2.4 mSv per year worldwide. A chest X-ray is roughly 0.1 mSv and an abdominal CT around 7 mSv. Occupational limits are typically 20 mSv per year averaged over five years. Acute effects begin around 500 mSv delivered quickly, and about 4 Sv whole-body is the median lethal dose without medical intervention. Chronic low doses carry statistical risk rather than immediate symptoms.
What is a roentgen and why is it still used?
The roentgen measures exposure, defined as the electrical charge liberated by ionisation in dry air, fixed at 2.58 × 10⁻⁴ C/kg. It survives because air ionisation is easy for a survey meter to measure directly. It is not a dose unit: converting it to gray or sievert needs an f-factor that depends on photon energy and on the absorbing material, roughly 0.0088 Gy per roentgen in air and closer to 0.0096 in soft tissue.
What is the radiation weighting factor?
A multiplier that converts absorbed dose into equivalent dose, reflecting how densely a given radiation deposits its energy. ICRP Publication 103 sets it at 1 for photons and electrons, 2 for protons, 20 for alpha particles and fission fragments, and a continuous energy-dependent function for neutrons that peaks around 20. Alpha emitters are relatively harmless outside the body and extremely dangerous once inhaled or ingested precisely because of that factor of 20.
Why does my body contain radioactivity?
Naturally occurring potassium-40 and carbon-14 make an average adult about 4,000 to 5,000 becquerels of intrinsic activity, roughly 0.1 microcuries. This contributes a fraction of a millisievert per year internally. It is a useful scale check: four thousand decays per second sounds alarming until you realise it describes every human being alive.