Radiation Converter (Exposure)

The Radiation Exposure Converter converts between units of ionizing radiation exposure, which measures the ionization produced in air by X-rays or gamma rays. The SI unit is coulombs per kilogram (C/kg), while the older unit is the roentgen (R), where 1 R = 2.58 x 10⁻⁴ C/kg.

Radiation exposure specifically refers to the amount of ionization that X-ray or gamma radiation produces in a specified mass of air. It is distinct from absorbed dose (gray) and equivalent dose (sievert). The roentgen was one of the first radiation measurement units, introduced in 1928, and named after Wilhelm Röntgen, discoverer of X-rays.

The roentgen is defined as the amount of X- or gamma radiation that produces ionization resulting in one electrostatic unit (esu) of charge in one cubic centimeter of air at STP. In SI terms, this equals 2.58 x 10⁻⁴ C/kg. The roentgen applies only to X-rays and gamma rays in air, not to other types of radiation or materials.

In radiation protection, the roentgen has been largely superseded by the sievert (for effective dose) and gray (for absorbed dose). However, roentgens are still used in some survey instruments and older regulations, particularly in the United States. Environmental background radiation is typically 5–20 µR/hr (0.05–0.2 mR/hr).

Medical X-ray exposures are typically in the range of 0.1–10 mR for dental films, 10–100 mR for chest X-rays, and 100–1,000 mR for CT scans. Emergency exposure limits for radiation workers are often stated as 25 R for lifesaving actions.