# 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]

## Contents

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
Gray
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

## References

1. U.S.NRC (06, 21, 2016). Gray (Gy) [Online]. Available: http://www.nrc.gov/reading-rm/basic-ref/glossary/gray-gy.html