Roentgen converter
Convert X-ray and gamma exposure between roentgen, C/kg and air kerma.
That's about the same as a chest X-ray.
What it means
How much exposure is that?
Information only. Medical figures are typical entrance exposures and vary widely with equipment and patient. For dose to people, use gray and sievert.
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Three things worth knowing
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1 R ≈ 8.76 mGy in air
And roughly 9.6 mGy in soft tissue for medical X-rays. The US still quotes survey meters in mR/h, where 1 mR/h is about 10 µSv/h.
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Named after Röntgen
Wilhelm Röntgen discovered X-rays in 1895, and the unit bearing his name was the first radiation unit, adopted in 1928. The SI replaced it with C/kg but never gave that a name.
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Exposure is not dose
The same roentgen of radiation deposits different energy in bone, fat and air, and does different harm. Convert to gray for energy absorbed and to sievert for health risk.
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Background
About radiation exposure
Exposure measures how strongly X-rays or gamma rays ionize the air they pass through. The roentgen is defined exactly as 2.58 × 10⁻⁴ coulombs of charge freed per kilogram of air.
It describes the radiation field, not what a body absorbs. For X-rays in soft tissue one roentgen comes to about 0.01 Gy, which is why old texts treat R, rad and rem as nearly interchangeable.