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