Rad (radiation unit)

"Rad (unit)" redirects here. Not to be confused with Rad (angular unit).
rad
Unit systemCGS units
Unit ofAbsorbed dose of ionizing radiation
Symbolrad
Conversions
1 rad in ...... is equal to ...
   SI base units   0.01 J⋅kg−1
   SI units   0.01 Gy
   CGS   100 erg/g

The rad is a unit of absorbed radiation dose, defined as 1 rad = 0.01 Gy = 0.01 J/kg.[1] It was originally defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by one gram of matter. The material absorbing the radiation can be human tissue, air, water, or any other substance.

It has been replaced by the gray (symbol Gy) in SI derived units, but is still used in the United States, although this is "strongly discouraged" in Chapter 5.2 of the Guide to the SI, which was written and published by the U.S. National Institute of Standards and Technology.[2] However, the numerically equivalent SI unit submultiple, the centigray (symbol cGy), is widely used to report absorbed doses within radiotherapy. The roentgen, used to quantify the radiation exposure, may be related to the corresponding absorbed dose by use of the F-factor.

  1. ^ International Bureau of Weights and Measures (2008). United States National Institute of Standards and Technology (ed.). The International System of Units (SI) (PDF). NIST Special Publication 330. Dept. of Commerce, National Institute of Standards and Technology. Retrieved September 1, 2018.
  2. ^ "NIST Guide to SI Units – ch.5.2 Units temporarily accepted for use with the SI". National Institute of Standards and Technology.