Radiation Dose Converter
Equivalent radiation dose is measured in sieverts in the metric system and in rem in older United States practice. One sievert equals 100 rem, so one millisievert is 100 millirem. Natural background exposure is roughly 3 millisieverts a year.
For scale: a chest X-ray is around 0.1 mSv, a transatlantic flight roughly 0.08 mSv, and natural background is about 3 mSv a year.
| Millisieverts | Microsieverts | Rem | Millirem |
|---|---|---|---|
| 0.1 mSv | 100 µSv | 0.01 rem | 10 mrem |
| 1 mSv | 1000 µSv | 0.1 rem | 100 mrem |
| 3 mSv | 3000 µSv | 0.3 rem | 300 mrem |
| 10 mSv | 10000 µSv | 1 rem | 1000 mrem |
| 20 mSv | 20000 µSv | 2 rem | 2000 mrem |
| 100 mSv | 100000 µSv | 10 rem | 10000 mrem |
How to convert sieverts to rem
Choose the units
Pick the unit your reading or badge report uses and the unit you need it in.
Enter the dose
Type the value into either field and the other converts live as you type.
Compare to everyday exposure
Use the note and table to place the number against a chest X-ray, a flight, or annual background.
Copy the result
Copy the converted dose into your log or report.
Why use this tool
Both unit families
The sievert family and the rem family convert between each other in either direction, including the milli and micro prefixes that dosimeters report.
Everyday exposures for scale
A chest X-ray, a long flight and annual background sit next to the result, which is the quickest way to catch a prefix error.
Equivalent dose only, on purpose
Gray and rad measure absorbed dose, a different quantity that needs a radiation weighting factor to relate, so they are excluded rather than assumed.
Micro to sievert in one step
Dosimeters usually read in microsieverts while limits are written in millisieverts, and that jump is where prefix mistakes happen.
Runs entirely in your browser
Nothing you type is uploaded or stored.
About this tool
Equivalent dose describes how much biological harm a given exposure to ionising radiation is expected to cause. The metric unit is the sievert, and the older unit still used in parts of United States practice is the rem, short for roentgen equivalent man. The relationship is fixed: one sievert equals exactly 100 rem, so one millisievert is 100 millirem and one microsievert is 0.1 millirem.
In practice almost nothing is measured in whole sieverts, because a sievert is an enormous dose. Personal dosimeters report microsieverts, occupational limits are written in millisieverts, and older United States paperwork uses millirem. Moving between those prefixes is where most mistakes happen, which is why this tool puts all five units in one list and converts in either direction as you type.
For scale: a chest X-ray is roughly 0.1 millisieverts, a transatlantic flight about 0.08 millisieverts, a CT scan of the abdomen several millisieverts, and natural background radiation averages around 3 millisieverts a year worldwide. Absorbed dose units, the gray and the rad, are deliberately not included here. They measure energy deposited per kilogram rather than biological effect, and converting them into sieverts requires a radiation weighting factor that is 1 for X-rays and gamma but 20 for alpha particles. For general unit work there is the unit converter and the metric prefix converter.
Frequently asked questions
- How many rem is one sievert?
- Exactly 100 rem. So 1 millisievert is 100 millirem, and 10 microsieverts is 1 millirem. The relationship is a fixed definition rather than a measured value.
- Why is gray not in the list?
- Gray measures absorbed dose, the energy deposited per kilogram of tissue, while sievert measures the biological effect of that energy. Converting between them needs a radiation weighting factor that depends on the type of radiation, so it cannot be done from the number alone.
- How much radiation is normal in a year?
- Natural background averages about 3 millisieverts a year, or 300 millirem, though it varies widely with altitude and local geology. Occupational limits for radiation workers are typically set at 20 millisieverts a year.
- What does a dosimeter usually read in?
- Microsieverts, because everyday doses are small. Since limits are written in millisieverts, a factor of 1,000 sits between what the device shows and what the paperwork asks for.
- Is this medical or safety advice?
- No. It converts between units and nothing more. Whether a dose is acceptable depends on context, regulation and the person, and those judgements belong to a qualified radiation protection professional.
- Is my data uploaded anywhere?
- No. The conversion runs in your browser and nothing you type leaves your device.
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