Radiation Dose Converter
Convert between sievert, mSv, µSv and rem.
Results update as you type.
This calculator provides estimates based on population research. Results are not medical advice. Consult a qualified healthcare provider before making health or nutrition decisions.
How it works
A radiation dose converter restates an equivalent radiation dose in a different unit, moving between the SI sievert and its millisievert and microsievert subdivisions, and the older rem still common in the United States. It reduces your figure to sieverts, the SI unit for equivalent and effective dose, then scales out to the unit you choose, so one mechanism covers medical imaging doses, occupational exposure limits, background radiation figures and safety reports alike. This matters because radiation dose is reported in different units depending on the country and era, and the numbers differ by a factor of a hundred. International and medical practice uses sieverts, usually as millisieverts for a scan or microsieverts for small everyday exposures; United States regulations and older literature use rem, where one rem is one-hundredth of a sievert. A chest scan quoted in millisieverts and an occupational limit quoted in rem cannot be compared until both share one unit, and getting that wrong by a factor of a hundred is a serious matter. The convert-through-sievert method is used because every dose unit has a fixed ratio to the sievert — one rem is exactly 0.01 Sv, one millisievert is a thousandth, one microsievert a millionth — so pivoting through it keeps results exact and needs only one factor per unit. This tool converts units of equivalent dose only; it does not assess health risk. Radiographers, health physicists, nuclear workers, researchers and students rely on a radiation dose converter whenever a figure arrives in an unfamiliar unit.
Convert to sievert via known factors, then to the target unit
The input is multiplied by its unit's fixed number of sieverts to express the dose in sieverts, then divided by the target unit's sievert value to complete the conversion. The metric prefixes milli and micro are exact powers of ten below the sievert, and one rem is defined as exactly 0.01 sievert, so every unit has a fixed ratio to the SI base, making the pivot exact for every pairing with one stored factor per unit.
Source:International System of Units (SI) — NIST
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter value, from and to.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Converted dose updates instantly as you type — no button to press.
Frequently asked questions
How do I convert sievert to rem?
Multiply the sievert figure by 100, since one sievert equals exactly 100 rem. So a 1 millisievert scan is 0.1 rem, and 5 mSv is 0.5 rem. To reverse it, divide rem by 100. The relationship is exact by definition, so only display rounding appears. Keeping the factor of a hundred straight is important, since a slip changes a dose figure dramatically.
What is a millisievert in everyday terms?
A millisievert is one-thousandth of a sievert and a convenient scale for medical and background doses. For rough context, natural background radiation is often a few millisieverts per year, and a chest X-ray is a small fraction of a millisievert, while a CT scan may be several millisieverts. This converter changes units only and does not evaluate whether any dose is safe; consult qualified guidance for that.
What is the difference between sievert and gray?
The gray measures absorbed dose, the raw energy deposited per kilogram of tissue, while the sievert measures equivalent or effective dose, which weights that energy by how harmful the radiation type and affected organs are. For many common exposures the numbers are similar, but they are conceptually different. This converter handles sievert-based equivalent-dose units and their rem counterpart, not the gray.
Why is rem still used?
Rem, standing for roentgen equivalent man, remains in use in the United States nuclear and regulatory context, and in older literature worldwide, even though the sievert is the official SI unit. Many US dose limits and instrument readouts are still stated in rem or millirem. Because one sievert is a hundred rem, converting between them is a routine need when comparing US and international figures.
Does this converter tell me if a dose is dangerous?
No. It only changes a dose figure between units of equivalent dose; it does not assess health risk, which depends on many factors including the exposure duration, the tissues involved and individual circumstances. For any question about whether an exposure is safe, consult a qualified health physicist, radiographer or medical professional and the relevant regulatory limits rather than relying on a unit conversion alone.