Radiation Exposure Converter

Radiation exposure measures how strongly X-rays or gamma rays ionize air: the electric charge they free in a mass of air. Its SI unit is the coulomb per kilogram (C/kg), and the older roentgen (R) is 2.58 × 10⁻⁴ C/kg. Survey meters and older X-ray equipment still show roentgens, often as mR/h.

Exposure describes the radiation field, not what a body absorbs. The absorbed dose is measured in grays, in the Radiation Absorbed Dose Converter. In soft tissue, an exposure of 1 R gives a dose of roughly 0.0096 Gy (0.96 rad), which is why the roentgen, the rad and the rem were often treated as about equal.

How to convert radiation exposure

Type a value into any field, and every other unit is calculated at once. For example, 5 R:

1. In C/kg: multiply by 0.000258.

   5 * 0.000258 = 0.00129 C/kg

2. In μC/kg: multiply by 258.

   5 * 258 = 1,290 μC/kg

Common conversions

Radiation exposure units

• Roentgen (R) The Roentgen is a legacy unit of radiation exposure used to quantify the amount of ionization produced by X-rays or gamma rays in a specific volume of air.
  Conversion Factor: 1 R = 2.58 × 10^(-4) C/kg = 0.000258 C/kg

• Coulomb/kilogram (C/kg): The Coulomb per kilogram is the SI unit of radiation exposure, representing the electric charge created in one kilogram of air by ionizing radiation.
  Conversion Factor: 1 C/kg = 3876 R

• Millicoulomb/kilogram (mC/kg): The Millicoulomb per kilogram is a smaller unit of exposure, equal to one thousandth of a Coulomb per kilogram.
  Conversion Factor: 1 mC/kg = 0.001 C/kg = 3.876 R

• Microcoulomb/kilogram (μC/kg): The Microcoulomb per kilogram is an even smaller unit, equivalent to one millionth of a Coulomb per kilogram.
  Conversion Factor: 1 μC/kg = 0.000001 C/kg = 0.003876 R

• Tissue Roentgen, Parker and Rep are old units from the early days of radiation protection, defined close to the Roentgen. This converter treats them as equal to it, at a ratio of 1:1.