Rads to grays
Type a value in rads to see it in grays straight away, or type in the second box to convert back.
Loading the tool…
Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Type the value in the rads box.
- Read the result in grays as you type, and pick the precision you need.
- Swap the direction to convert back, or copy the result.
How it is calculated
Gy = rad × 0.01
Multiply the value in rads by 0.01 to get grays.
Example
To convert 25 rad to grays: 25 × 0.01 = 0.25 Gy.
Conversion table
| Rads (rad) | Grays (Gy) |
|---|---|
| 1 | 0.01 |
| 2 | 0.02 |
| 3 | 0.03 |
| 5 | 0.05 |
| 10 | 0.1 |
| 20 | 0.2 |
| 25 | 0.25 |
| 50 | 0.5 |
| 100 | 1 |
| 250 | 2.5 |
| 500 | 5 |
| 1,000 | 10 |
About the units
- Rad
- An older unit of absorbed dose equal to 100 erg per gram, exactly 0.01 gray, still seen in US references.
- Gray
- The SI unit of absorbed dose, equal to one joule of radiation energy absorbed per kilogram of matter.
Limits and caveats
- Results are rounded for display and computed with the browser's floating point precision (about 15 significant digits).
- Both unit factors are exact by their official definitions.
Questions about this tool
How many grays are in one rad?
1 rad = 0.01 Gy exactly.
How do I convert rads to grays?
Use Gy = rad × 0.01. For example, 25 rad = 0.25 Gy.
How many rads are in one gray?
1 Gy = 100 rad.
What is the difference between gray and sievert?
The gray measures energy actually absorbed, while the sievert adds a weighting for the type of radiation and its biological effect. For X-rays and gamma rays the weighting is 1, so 1 Gy corresponds to about 1 Sv.
Why do radiotherapy teams use centigrays?
A centigray equals exactly one rad, so the switch from rad to the SI unit kept the familiar numbers.