Radiation Dose Converter
ScienceConvert radiation dose units between sievert, gray, rad, and rem — used for medical imaging, occupational safety, and nuclear science dose limits.
From
To
All conversionsfor 1 Millisievert (mSv)
| Sievert (Sv) | 0.001 |
| Millisievert (mSv) | 1 |
| Microsievert (µSv) | 1000 |
| Gray (Gy) — absorbed dose | 0.001 |
| Milligray (mGy) — absorbed dose | 1 |
| Rem (equivalent dose) | 0.1 |
| Millirem (mrem) | 100 |
| Rad (absorbed dose) | 0.1 |
What is a Radiation Dose?
The Radiation Dose Converter converts between the units used to measure how much ionising radiation a person or object has absorbed — sievert, gray, rad, and rem, along with their common sub-units (millisievert, millirem, milligray). These units appear constantly in medical imaging reports, occupational radiation safety logs, and nuclear science contexts, but the US commonly uses the older CGS-based rem and millirem while most of the rest of the world uses the SI sievert, making conversion between them a routine necessity.
This converter treats gray and sievert as numerically equivalent, and rad and rem as numerically equivalent — accurate for X-rays, gamma rays, and beta particles, which cover the overwhelming majority of medical and occupational exposure scenarios. If you need decay activity rather than absorbed dose, the Radioactivity Converter handles curie and becquerel instead.
How to use this Radiation Dose calculator
- Choose your starting unit from the source dropdown — for example, "Millisievert (mSv)".
- Enter the numeric dose value in the input field.
- Choose your target unit from the destination dropdown — for example, "Millirem (mrem)".
- Read the converted result, which updates instantly as you type or change units.
- Use the swap (⇅) button if you need to reverse the conversion direction.
- Use the copy button to grab the result for a dose log, medical report, or safety record.
Formula & Methodology
The converter's base unit is the sievert (Sv). Every supported unit has a fixed multiplier to sievert: - 1 millisievert (mSv) = 0.001 Sv - 1 microsievert (µSv) = 0.000001 Sv - 1 gray (Gy) = 1 Sv (assuming a radiation weighting factor of 1 — accurate for X-rays, gamma, and beta radiation) - 1 milligray (mGy) = 0.001 Sv - 1 rem = 0.01 Sv - 1 millirem (mrem) = 0.00001 Sv - 1 rad = 0.01 Sv (under the same weighting-factor-1 assumption as gray) Any conversion follows: Result = Input × (toBase of source unit ÷ toBase of target unit) Worked example — converting 5 mSv (a typical annual medical imaging dose) to millirem: Result = 5 × (0.001 ÷ 0.00001) = 5 × 100 = 500 millirem This confirms the standard 100:1 relationship between millisievert and millirem used throughout radiation safety documentation.
Frequently Asked Questions
Gray measures absorbed dose — the raw amount of radiation energy deposited in tissue per kilogram — while sievert measures equivalent dose, which weights the absorbed dose by how biologically damaging that type of radiation is. For X-rays, gamma rays, and beta particles the weighting factor is 1, so gray and sievert are numerically equal; for alpha particles and neutrons, the weighting factor is higher, meaning the same absorbed dose in gray produces a larger equivalent dose in sievert.
Enter your value with 'Millisievert (mSv)' as the source unit and 'Millirem (mrem)' as the target — one millisievert equals 100 millirem, since rem is a smaller (CGS-based) unit than sievert. This conversion is common when comparing a US medical report (often in mrem) against an international one (typically in mSv).
A rem is the CGS-system unit of equivalent radiation dose, predating the SI sievert, and one sievert equals exactly 100 rem. The rem (and its subunit, the millirem) is still the standard unit used in US occupational radiation safety and medical dose reporting, while most of the rest of the world uses sievert.
A standard chest X-ray delivers approximately 0.1 mSv (10 mrem) of effective dose, roughly equivalent to about 10 days of natural background radiation exposure. Enter 0.1 with 'Millisievert (mSv)' as the source to see this converted into rem, microsievert, or gray.
Rad measures absorbed dose (the CGS equivalent of gray), while rem measures equivalent dose (the CGS equivalent of sievert) — the same relationship that exists between gray and sievert in the SI system. For radiation types with a weighting factor of 1 (X-rays, gamma, beta), 1 rad numerically equals 1 rem.
Enter your value with 'Rad (absorbed dose)' as the source unit and 'Gray (Gy) — absorbed dose' as the target — one rad equals 0.01 gray, so 100 rad equals 1 gray. This is the absorbed-dose equivalent of the rem-to-sievert relationship.
In the US, the NRC sets an annual occupational limit of 50 mSv (5,000 mrem) effective dose for radiation workers, while many other countries and the ICRP recommend a lower limit of 20 mSv per year averaged over five years. This converter helps translate a worker's cumulative dose log between mSv and mrem to check against whichever limit applies.
This converter uses a 1:1 relationship between gray and sievert, which is accurate for X-rays, gamma rays, and beta particles — the radiation types involved in the vast majority of medical imaging and typical occupational exposure. For alpha particles or neutron radiation, the true equivalent dose in sievert is higher than the absorbed dose in gray by a radiation-specific weighting factor, which this general converter does not apply.
The average person receives roughly 2 to 3 mSv (200–300 mrem) per year from natural background sources like radon gas, cosmic rays, and naturally occurring radioactive materials in soil and rock. This is a useful reference point for putting medical or occupational dose values into everyday context.
No — the [Radioactivity Converter](/radioactivity-converter/) converts units of radioactive decay activity (curie, becquerel), which measure how many atoms in a radioactive source decay per second, while this converter handles dose units (sievert, gray, rad, rem), which measure how much radiation energy a person or object actually absorbs. A highly active source can deliver a small or large dose depending on distance, shielding, and exposure time.
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