Rad (radiation unit)

rad
rad
Unit system	CGS units
Unit of	Absorbed dose of ionizing radiation
Symbol	rad
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It has been replaced by the gray (symbol Gy) in SI derived units, but is still used in the United States, although this is "strongly discouraged" in Chapter 5.2 of the Guide to the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.

^ 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.
^ "NIST Guide to SI Units – ch.5.2 Units temporarily accepted for use with the SI". National Institute of Standards and Technology.

[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.

[1]

[2]