Gray is absorbed dose in joules per kilogram.
Grays to Megagrays Converter — Gy to MGy
Convert Gray (Gy) to Megagray (MGy) using the exact conversion factor (1 gray = 0.000001 megagray). See the formula, worked examples, conversion table, history, and common uses.
Grays to Megagrays 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.
Megagray is 1000000 gray units.
Result = input x 1 / 1e+6.
Absorbed Dose units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Grays to Megagrays
Gray and Megagray 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
megagrays = grays × 0.000001
This factor comes from each unit's defined relationship to the category's base unit: 1 gray equals 1 base unit, and 1 megagray equals 1000000 base units, so dividing one by the other gives the direct gray-to-megagray factor of 0.000001.
Simple example
1 Gy × 0.000001 = 0.000001 MGy
1 gray = 0.000001 megagrays.
Real-world example
10 Gy × 0.000001 = 0.00001 MGy
10 grays = 0.00001 megagrays.
Conversion table
| Gray (Gy) | Megagray (MGy) |
|---|---|
| 0.001 Gy | 1e-9 MGy |
| 0.01 Gy | 1e-8 MGy |
| 0.1 Gy | 1e-7 MGy |
| 1 Gy | 0.000001 MGy |
| 10 Gy | 0.00001 MGy |
| 100 Gy | 0.0001 MGy |
Reverse conversion: Megagray to Gray
0.000001 MGy × 1000000 = 1 Gy
0.000001 megagrays = 1 gray.
grays = megagrays × 1000000
For a page dedicated to this direction, see Megagray 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 Megagray (MGy)
Megagray is 1000000 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 megagrays are in 1 gray?
1 gray equals 0.000001 megagrays, using the exact defined conversion factor rather than an estimate.
How do I convert gray to megagray?
Multiply the gray value by 0.000001. The converter above does this instantly to whatever precision you set.
How do I convert megagray back to gray?
Use the reverse factor: 1 megagray equals 1,000,000 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 megagray?
Megagray (MGy) is a unit of radiation.
Is the gray to megagray conversion exact?
Yes. Both gray and megagray are defined by fixed standards rather than physical artifacts, so the factor of 0.000001 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