Gray is absorbed dose in joules per kilogram.
Grays to Kilograys Converter — Gy to kGy
Convert Gray (Gy) to Kilogray (kGy) using the exact conversion factor (1 gray = 0.001 kilogray). See the formula, worked examples, conversion table, history, and common uses.
Grays to Kilograys converter
Converter
Radiation Converter
Convert radioactivity, absorbed dose, and equivalent dose units by compatible radiation family.
Context values
Some unit families need one extra value for a physically accurate result.
Kilogray is 1000 gray units.
Result = input x 1 / 1000.
Absorbed Dose units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Grays to Kilograys
Gray and Kilogray both belong to the radiation-measurement family, though radiation quantities fall into genuinely distinct categories: absorbed dose (gray, rad) measures energy deposited in matter, equivalent dose (sievert, rem) weights that for biological harm, and activity (becquerel, curie) measures how often a radioactive source decays — this page only converts between units of the same kind. Gray is most often used for radiation therapy dose prescriptions in medicine.
Formula
kilograys = grays × 0.001
This factor comes from each unit's defined relationship to the category's base unit: 1 gray equals 1 base unit, and 1 kilogray equals 1000 base units, so dividing one by the other gives the direct gray-to-kilogray factor of 0.001.
Simple example
1 Gy × 0.001 = 0.001 kGy
1 gray = 0.001 kilograys.
Real-world example
10 Gy × 0.001 = 0.01 kGy
10 grays = 0.01 kilograys.
Conversion table
| Gray (Gy) | Kilogray (kGy) |
|---|---|
| 0.001 Gy | 0.000001 kGy |
| 0.01 Gy | 0.00001 kGy |
| 0.1 Gy | 0.0001 kGy |
| 1 Gy | 0.001 kGy |
| 10 Gy | 0.01 kGy |
| 100 Gy | 0.1 kGy |
Reverse conversion: Kilogray to Gray
0.001 kGy × 1000 = 1 Gy
0.001 kilograys = 1 gray.
grays = kilograys × 1000
For a page dedicated to this direction, see Kilogray to Gray.
Understanding the Gray
Gray (Gy) measures absorbed radiation dose. The SI derived unit of absorbed radiation dose, equal to one joule of radiation energy absorbed per kilogram of matter. It is classified as a SI derived unit.
Where it's used: Universal — SI derived unit used worldwide in medicine and radiation protection
Gray vs. sievert. The gray measures physically absorbed energy; the sievert measures equivalent dose, which weights the gray value for how biologically damaging a given type of radiation is. The same absorbed dose in gray can correspond to different sievert values depending on the radiation type.
Uses of the Gray today
- Radiation therapy dose prescriptions in medicine
- Radiation safety and occupational dose monitoring
- Nuclear and radiological research
History of the Gray
The gray is named after Louis Harold Gray (1905–1965), a British physicist who pioneered the physics of radiation dosimetry and its biological effects, and was adopted by the CGPM as an SI derived unit in 1975.
Historical origin. Gray was not the invention of a single named person; it developed through the process described above.
Understanding the Kilogray (kGy)
Kilogray is 1000 gray units.
Gray — sources
- BIPM SI Brochure, 9th edition — Official definition of the gray as an SI derived unit.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many kilograys are in 1 gray?
1 gray equals 0.001 kilograys, using the exact defined conversion factor rather than an estimate.
How do I convert gray to kilogray?
Multiply the gray value by 0.001. The converter above does this instantly to whatever precision you set.
How do I convert kilogray back to gray?
Use the reverse factor: 1 kilogray equals 1,000 grays. You can also use the swap control in the converter above to flip the direction instantly.
What is a gray?
Gray (Gy) measures absorbed radiation dose. The SI derived unit of absorbed radiation dose, equal to one joule of radiation energy absorbed per kilogram of matter. It is classified as a SI derived unit.
What is a kilogray?
Kilogray (kGy) is a unit of radiation.
Is the gray to kilogray conversion exact?
Yes. Both gray and kilogray are defined by fixed standards rather than physical artifacts, so the factor of 0.001 used above is exact to as many digits as you choose to display.
What is the difference between gray vs. sievert?
The gray measures physically absorbed energy; the sievert measures equivalent dose, which weights the gray value for how biologically damaging a given type of radiation is. The same absorbed dose in gray can correspond to different sievert values depending on the radiation type.
Where is the gray still used today?
Universal — SI derived unit used worldwide in medicine and radiation protection