Radiation Exposure Converter
Convert between coulombs per kilogram, millicoulombs per kilogram, roentgens, milliroentgens and microroentgens.
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Radiation Exposure units
Every unit below converts to every other one in the calculator. Values are relative to the base unit, the coulomb per kilogram (C/kg).
| Unit | Symbol | System | Value |
|---|---|---|---|
| Coulomb per kilogram | C/kg | SI | Base unit |
| Millicoulomb per kilogram | mC/kg | SI | = 0.001 C/kg |
| Roentgen | R | other | = 0.000258 C/kg |
| Milliroentgen | mR | other | = 2.58e-7 C/kg |
| Microroentgen | µR | other | = 2.58e-10 C/kg |
Coulomb per kilogram quick reference
| Coulomb per kilogram | Roentgen |
|---|---|
| 1 C/kg | ≈ 3875.968992 R |
| 10 C/kg | ≈ 38759.68992 R |
| 100 C/kg | ≈ 387596.8992 R |
| 1000 C/kg | ≈ 3875968.992 R |
Among the 5 radiation exposure units on this page, the smallest is the microroentgen (µR) and the largest is the coulomb per kilogram (C/kg).
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About radiation exposure units
Exposure measures how strongly X-rays or gamma rays ionize air: the electric charge they produce per kilogram of air. The SI unit is the coulomb per kilogram (C/kg); there is no special SI name for it.
The older roentgen (R) is exactly 2.58 × 10⁻⁴ C/kg, so 1 C/kg is about 3876 R. Exposure is defined only for X-rays and gamma rays in air. It is not an absorbed dose: 1 R deposits roughly 8.8 mGy in air, and the dose in other materials differs.
Frequently asked questions
- How many coulombs per kilogram are in a roentgen?
- Exactly 0.000258 C/kg (2.58 × 10⁻⁴), or 0.258 mC/kg.
- Can I convert roentgens to grays or sieverts?
- Not exactly with a single factor. Roentgens measure ionization in air, while grays and sieverts measure dose in a material or the body. In air, 1 R corresponds to roughly 8.8 mGy.
- How many roentgens are in one coulomb per kilogram?
- One coulomb per kilogram ≈ 3875.968992 R (roentgens).