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Radiation Dose Converter

Science

Convert radiation dose units between sievert, gray, rad, and rem — used for medical imaging, occupational safety, and nuclear science dose limits.

Reviewed by the thecalcu.com team · Last updated July 8, 2026

From
To
All conversionsfor 1 Millisievert (mSv)
Sievert (Sv)0.001
Millisievert (mSv)1
Microsievert (µSv)1000
Gray (Gy) — absorbed dose0.001
Milligray (mGy) — absorbed dose1
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.

Why Use a Radiation Dose Converter?

A patient reviewing a CT scan report might see a dose in millisievert, while a US occupational safety log tracks cumulative exposure in millirem, comparing the two, or checking either against a published annual limit, requires converting between unit systems that differ by a factor of 100 at every level. Getting that conversion wrong by a factor of 10 or 100 is a meaningful error when the numbers involved are safety thresholds.

This converter handles that instantly across sievert, gray, rad, and rem and their common sub-units. It's particularly useful for radiation workers tracking cumulative annual dose against regulatory limits that may be published in a different unit than their dosimeter badge reports.

Who Should Use This Converter?

  • Radiologic technologists and medical physicists converting patient dose reports between mSv and mrem for different reporting standards.
  • Radiation safety officers tracking occupational worker dose against annual limits published in either sievert or rem-based units.
  • Nuclear science and engineering students learning the relationship between absorbed dose (gray/rad) and equivalent dose (sievert/rem).
  • Patients and caregivers trying to understand a medical imaging dose report by comparing it to familiar reference points like a chest X-ray or annual background exposure.
  • Nuclear plant and industrial radiography workers whose dosimeter badges report in a different unit than their facility's internal safety documentation.

What Insights Does the Radiation Dose Converter Give You?

The main output is the converted dose value in your chosen target unit, calculated from the fixed relationship between each unit and the base sievert value. Because sievert/gray and rem/rad each represent a factor-of-100 jump between the SI and CGS systems, the converter makes it immediately clear how a value like "500 mrem" translates to the more internationally familiar "5 mSv."

Use the FAQ reference points above, a chest X-ray (about 0.1 mSv), annual background radiation (2–3 mSv), and the US occupational limit (50 mSv), to put any converted value into real-world context.

How to use this Radiation Dose calculator

  1. Choose your starting unit from the source dropdown, for example, "Millisievert (mSv)".
  2. Enter the numeric dose value in the input field.
  3. Choose your target unit from the destination dropdown, for example, "Millirem (mrem)".
  4. Read the converted result, which updates instantly as you type or change units.
  5. Use the swap (⇅) button if you need to reverse the conversion direction.
  6. Use the copy button to grab the result for a dose log, medical report, or safety record.
Show formula & methodology ↓Show less ↑

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.

Related Tools

You may also find these useful: CGS to SI Units Converter, Energy Converter.

Frequently Asked Questions

What is the difference between sievert and gray?
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.
How do I convert millisievert to millirem?
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).
What is a rem, and how does it relate to a sievert?
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.
What is a typical radiation dose from a chest X-ray?
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.
What is the difference between rad and rem?
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.
How do I convert rad to gray?
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.
What is the annual radiation dose limit for occupational workers?
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.
Why does this converter treat gray and sievert as numerically equal?
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.
What is natural background radiation exposure per year?
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.
Is this the same as the Radioactivity Converter?
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.
Also known as
sievert to remmillirem to microsievertrad to graymrem to msvradiation dose converterrem to sievert