Radiation Dose Converter
Convert between radiation units: dose (Sv, mSv, µSv, rem, mrem), absorbed dose (Gy, rad), exposure (R, C/kg) and activity (Bq, Ci, dpm). Dose results are put in context with everyday references such as a chest X-ray or a year of natural background.
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How to use the Radiation Dose Converter
- Choose the quantity: dose (sieverts, rem), absorbed dose (grays, rads), exposure (roentgens) or activity (becquerels, curies).
- Type the value and pick the unit you are converting from.
- Pick the target unit in the To menu and press Convert.
- Read the result and the full list of equivalent units. For doses, check the comparison with everyday references.
- Copy the results or download the table as CSV.
Radiation units explained
Radiation is described with four different quantities, and each has an SI unit and an older traditional unit still common in the United States. Converting only makes sense inside one quantity: you can turn sieverts into rem, but not becquerels into sieverts without knowing the isotope, the exposure route and the time involved.
| Quantity | What it measures | SI unit | Traditional unit | Conversion |
|---|---|---|---|---|
| Activity | How many atoms decay each second in a source | becquerel (Bq) | curie (Ci) | 1 Ci = 3.7 × 10¹⁰ Bq |
| Exposure | Ionization produced in air by X-rays or gamma rays | coulomb per kilogram (C/kg) | roentgen (R) | 1 R = 2.58 × 10⁻⁴ C/kg |
| Absorbed dose | Energy deposited per kilogram of material | gray (Gy = J/kg) | rad | 1 Gy = 100 rad |
| Equivalent / effective dose | Absorbed dose weighted for radiation type and body tissue (health-related risk) | sievert (Sv) | rem | 1 Sv = 100 rem |
Quick rules: 1 mSv = 100 mrem, 1 µSv = 0.1 mrem, 1 mGy = 100 mrad, 1 mCi = 37 MBq, 1 Bq = 60 dpm. Dose rates such as µSv/h convert exactly the same way as the dose units: 0.5 µSv/h = 0.05 mrem/h.
Typical doses for comparison
Effective doses below are rounded, commonly published typical values (radiology and health physics references, U.S. NCRP and NRC, and UNSCEAR for the world average). Individual exams, flights and locations can be well above or below these figures.
| Source | mSv | mrem | µSv |
|---|---|---|---|
| Eating one banana (potassium-40), often quoted as the "banana equivalent dose" | 0.0001 | 0.01 | 0.1 |
| Dental intraoral X-ray | 0.005 | 0.5 | 5 |
| Coast-to-coast U.S. flight | ≈0.035 | ≈3.5 | ≈35 |
| Chest X-ray (single view) | 0.1 | 10 | 100 |
| U.S. annual limit for members of the public from licensed operations | 1 | 100 | 1,000 |
| Head CT scan | ≈2 | ≈200 | ≈2,000 |
| Worldwide average natural background per year | 2.4 | 240 | 2,400 |
| U.S. average from all sources per year (natural + medical + other) | ≈6.2 | ≈620 | ≈6,200 |
| U.S. annual occupational limit for radiation workers (whole body) | 50 | 5,000 | 50,000 |
Tips for reading radiation numbers
- Check the prefix carefully. mSv (milli, one thousandth) and µSv (micro, one millionth) differ by a factor of 1,000. Survey meters often read in µSv/h or mR/h.
- Dose vs dose rate. A reading in µSv/h is a rate. Multiply by the hours spent there to get a dose: 0.2 µSv/h for 24 hours is 4.8 µSv.
- Roentgen to rem shortcut. For X-rays and gamma rays, 1 R of exposure gives roughly 1 rad of tissue dose and about 1 rem, which is why older documents often treat R, rad and rem as interchangeable. They are not identical, so use the right unit for precise work.
- Radon in homes is reported as activity concentration, usually pCi/L in the U.S. and Bq/m³ elsewhere. 1 pCi/L = 37 Bq/m³, so the U.S. EPA action level of 4 pCi/L is 148 Bq/m³.
Frequently asked questions
How do you convert sieverts to rem?
Multiply by 100. 1 Sv = 100 rem, 1 mSv = 100 mrem and 1 µSv = 0.1 mrem. To go from rem to sieverts, divide by 100 (1 rem = 10 mSv).
What is the difference between gray and sievert?
The gray (Gy) measures absorbed dose: energy deposited per kilogram (1 Gy = 1 J/kg). The sievert (Sv) is equivalent or effective dose: the absorbed dose weighted for the type of radiation and the organs exposed. For X-rays and gamma rays the weighting factor is 1, so 1 Gy gives about 1 Sv.
How many rad are in a gray?
1 Gy = 100 rad, so 1 rad equals 1 centigray (cGy) or 10 mGy.
How do you convert curies to becquerels?
Multiply by 3.7 × 10^10. 1 Ci = 37 GBq, 1 mCi = 37 MBq, 1 µCi = 37 kBq and 1 pCi = 0.037 Bq.
What is dpm in radiation?
dpm means disintegrations per minute, a count of radioactive decays. Since 1 Bq is one decay per second, 1 Bq = 60 dpm and 1 µCi = 2,220,000 dpm.
What is a roentgen in C/kg?
The roentgen is defined as exactly 2.58 × 10^-4 coulombs of ionization per kilogram of air. It measures exposure from X-rays and gamma rays in air, not the dose a person receives; 1 R corresponds to roughly 8.76 mGy absorbed in air.
How much radiation is a chest X-ray?
A single-view chest X-ray gives roughly 0.1 mSv (10 mrem), roughly what you get from 10 to 15 days of average natural background radiation. Actual doses depend on the equipment and the patient.
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