Gray (Gy)
The gray (Gy) is the SI unit of absorbed dose: one joule of radiation energy deposited per kilogram of matter. Radiotherapy delivers about 2 Gy per session.
Symbol: Gy
Quantity: absorbed dose of ionising radiation
SI relation: Gy is the coherent SI unit of absorbed dose.
Derivation: 1 Gy = 1 J of absorbed energy per kg.
Exact: yes, by definition
Typical uses
- Radiotherapy prescriptions
- Radiation processing and sterilisation (kGy)
- Dosimetry
Convert grays to other units
| Conversion | 1 Gy equals | Reverse |
|---|---|---|
| gray to milligray | 1000 mGy | milligray to gray |
| gray to rad | 100 rad | rad to gray |
| gray to microgray | 1000000 µGy | microgray to gray |
| gray to centigray | 100 cGy | centigray to gray |
| gray to kilogray | 0.001 kGy | kilogray to gray |
| gray to millirad | 100000 mrad | millirad to gray |
Open the Absorbed Radiation Dose Converter to convert any value between all units.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 4 (becquerel, gray, sievert, lux) and Table 2 (candela).
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Gray (Gy). Retrieved October 25, 2026, from https://scientificconverters.com/units/gray/
IEEE
Scientific Converters, "Gray (Gy)," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/units/gray/