Skip to content
ToolBoxGenie

Radiation Converter

Converters · Added 15 August 2026

Convert radiation units within five separate quantities: equivalent dose, absorbed dose, activity, dose rate and exposure. These measure genuinely different things and are not interconvertible, so the tool makes you choose the quantity first — there is deliberately no path from becquerels to sieverts, because no unit converter has the information that conversion would require.

What are you measuring?

These five quantities are not interchangeable, so each converts only within itself. Becquerels cannot be turned into sieverts without knowing the isotope, the distance, the shielding and the exposure time, and no unit converter can supply those.

Result

1 mSv in millirem

100 mrem

1 mSv = 100 mrem

The same value in every unit

Sievert (Sv)
0.001
Millisievert (mSv)
1
Microsievert (µSv)
1,000
Nanosievert (nSv)
1,000,000
Rem (rem)
0.1
Millirem (mrem)
100
Microrem (µrem)
100,000

Equivalent dose weights absorbed dose by how biologically damaging the radiation type is. For X-rays, gamma rays and beta particles that weighting factor is 1, so grays and sieverts come out numerically equal; for alpha particles it is 20, so they do not.

How to use the radiation converter

  1. 1Choose which quantity you are working in — the units on your instrument or report will tell you.
  2. 2Enter the value and pick the unit it is in.
  3. 3Choose the unit you want; the result and a full table appear immediately.
  4. 4Use dose rate for a survey meter reading, and equivalent dose for a total received.
  5. 5Swap the units to reverse the conversion.

Examples

Equivalent dose, SI to legacy

Input
1 mSv
Result
100 mrem

The sievert replaced the rem; one sievert is exactly 100 rem.

Source activity

Input
1 mCi
Result
37 MBq

The curie is defined as exactly 3.7 × 10¹⁰ becquerels.

A survey meter reading

Input
0.15 µSv/h
Result
15 µrem/h

Dose rate is a rate — multiply by hours of exposure to get a dose.

About the radiation converter

Five quantities, and why keeping them apart matters

Radiation measurement is unusual in having several distinct quantities that all get loosely called 'radiation levels'. Activity, in becquerels or curies, describes a source: how many atoms are decaying per second. It says nothing about whether anyone is being exposed.

Absorbed dose, in grays or rads, describes energy deposited per unit mass in a material. Equivalent dose, in sieverts or rems, weights that by radiation type to reflect biological damage; effective dose weights it again by which organs were involved. Exposure, in coulombs per kilogram or roentgens, is an older quantity measuring ionisation produced in air, applicable to X-rays and gamma rays only.

Dose rate is any of the dose quantities divided by time, and it is what a survey meter displays. Confusing a rate with a total is the most common practical mistake: 5 µSv/h is a rate, and what it amounts to depends entirely on how long you stand there.

Why the older units persist

The curie was defined in 1910 as approximately the activity of one gram of radium-226 and later fixed at exactly 3.7 × 10¹⁰ decays per second. The roentgen, rad and rem followed from similar practical origins in early radiology and health physics. All of them were established before the international system settled on its coherent replacements.

The SI units are cleaner. A becquerel is one decay per second — no reference to any particular element. A gray is one joule per kilogram, connecting dose directly to energy. The sievert shares that definition with a dimensionless weighting factor applied. Each is defined from first principles rather than from a sample of a substance.

The older units survive mostly through installed practice: US regulations, instruments calibrated decades ago, and a large body of literature written in them. The awkward consequence is that a figure quoted without units, or with the wrong family assumed, can be out by a factor of a hundred — which is exactly the gap between a sievert and a rem. Reading the unit carefully is not pedantry here; it is the difference between two very different numbers.

Frequently asked questions

Why can't I convert becquerels to sieverts?
Because they measure different physical quantities. A becquerel counts decays per second inside a source; a sievert describes the biological effect of a dose received by tissue. Getting from one to the other requires the isotope involved, the type and energy of radiation it emits, the distance and shielding, the exposure time and whether the material is inside or outside the body — plus a published dose-conversion coefficient for that specific scenario. None of that is unit conversion, and a tool that offered the conversion anyway would be producing a fabricated number.
What is the difference between a gray and a sievert?
A gray is absorbed dose: energy deposited per kilogram of tissue, one joule per kilogram. A sievert is equivalent dose: that same absorbed dose weighted by how biologically damaging the radiation type is. For X-rays, gamma rays and beta particles the weighting factor is 1, so the two are numerically equal. For alpha particles it is 20, so one gray of alpha exposure is twenty sieverts. The gray describes the physics; the sievert attempts to describe the consequence.
Why are there two sets of units for everything?
The rad, rem, curie and roentgen are the older units, still in common use in the United States. The gray, sievert and becquerel are their SI replacements, adopted internationally from the 1970s onwards. Both sets remain in circulation, so instruments, regulations and literature from different eras and countries use different ones. The relationships are exact — 1 Gy = 100 rad, 1 Sv = 100 rem, 1 Ci = 3.7 × 10¹⁰ Bq — so conversion is straightforward once you know which family you are in.
Does this tool tell me whether a reading is safe?
No. It converts units and nothing more. Whether any particular dose or dose rate matters depends on the exposure pathway, the duration, who is exposed and the regulatory framework that applies — questions for a qualified radiation protection adviser and the relevant national standards, not for a converter. Deliberately, no exposure limits or safety thresholds appear anywhere on this page.

Related tools