Gray

The gray or Gy is the official SI unit for absorbed dose which measures the amount of ionizing radiation that has been absorbed by any material.[1] However, Gy can be used to measure any form of radiation except for the biological effects of the different forms of radiations.[2] Gy is measured in joules per kilogram or J/kg. Before the establishment of Gy as the official SI unit for absorbed dose, the non-SI unit radiation absorbed dose or rad was used. One gray is equivalent to one hundred rads or 1 Gy = 100 rad.[3]

Radiation-related quantities

The following table shows radiation quantities in SI and non-SI units.[4][5]

Quantity Name Symbol Unit System
Exposure Roentgen R 2.58x10-6 C/kg Non-SI
Absorbed Dose Rad
Gray
rad
Gy
10-2 Gy
Jkg-1
Non-SI
SI
Activity Curie
Becquerel
Ci
Bq
3.7x1010 Bq
s-1
Non-SI
SI
Dose Equivalent Roentgen Equivalent Man
Sievert
rem
Sv
10-2 Sv
Jkg-1
Non-SI
SI

Gray Unit Converter



For Further Reading

References

  1. U.S.NRC (06, 21, 2016). Gray (Gy) [Online]. Available: http://www.nrc.gov/reading-rm/basic-ref/glossary/gray-gy.html
  2. OCW.MIT, Lecture Notes, “Electromagnetic Radiation”, Fall 2004. [Online]. Available: http://ocw.mit.edu/courses/nuclear-engineering/22-55j-principles-of-radiation-interactions-fall-2004/lecture-notes/intro_absorb_dos.pdf
  3. U.S.NRC(06, 21. 2016). Rad (radiation absorbed dose) [Online]. Available: http://www.nrc.gov/reading-rm/basic-ref/glossary/rad-radiation-absorbed-dose.html
  4. NIST. (2016, February 10). Chapter 5. Guide to the SI, Units Outside the SI [Online]. Available: http://www.nist.gov/pml/pubs/sp811/sec05.cfm
  5. NIST. (2016, February 19). Chapter 4. Guide to the SI, The Two Classes of SI Units and the SI Prefixes [Online]. Available: http://www.nist.gov/pml/pubs/sp811/sec04.cfm

Authors and Editors

Allison Campbell, Celeste Pomerantz, Jason Donev
Last updated: June 25, 2018
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