This page converts millirads into grays using the factor 1e-05, and shows the reverse figure alongside it. Both units measure the energy a radiation field deposits per kilogram, which is why one number does the whole job.
Millirads appear on older survey meters and in US regulatory limits. The gray is the SI unit of absorbed radiation dose: one joule of energy deposited per kilogram of matter.
Grays are not sieverts. The gray measures energy deposited per kilogram; the sievert weights that energy by how biologically damaging the particular radiation is. For X-rays and gamma the weighting factor is 1 and the numbers coincide, but for alpha particles it is 20, so converting between them blindly can be wrong by that factor. Below the calculator there is a step table for the values people look up most, and a second table putting real the energy a radiation field deposits per kilogram figures into grays so the number you get has something to be compared against.
The formula
millirads- The amount you are converting, in millirads
1e-05- The exact number of grays in one millirad
grays- The converted result
How it works, step by step
- Enter the value in millirads.
- It is multiplied by 1e-05, the exact factor between the two units.
- The answer is shown in grays, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
Chest X-ray: 10 mrad in grays
At 10 mrad (chest x-ray), the same quantity in grays is 10 × 1e-05 = 0.0001 Gy. One millirad is 1e-05 grays, so the numbers shrink as expected.
Radiotherapy fraction: 2e+05 mrad in grays
At 2e+05 mrad (radiotherapy fraction), the same quantity in grays is 2e+05 × 1e-05 = 2 Gy. One millirad is 1e-05 grays, so the numbers shrink as expected.
How to read your score
Frequently asked questions
How many grays are in one millirad?
Exactly 1e-05. Every figure on this page is that one number multiplied by your input, so the only rounding is at the display step.
What is the formula to convert millirads to grays?
grays = millirads × 1e-05. Reversed, millirads = grays ÷ 1e-05, which is the same as multiplying by 100,000.
Which is the bigger unit, the millirad or the gray?
The gray. One millirad is only 1e-05 of a gray, so it takes 100,000 millirads to make one gray.
What does this quantity actually measure?
Both units measure the energy a radiation field deposits per kilogram. That is why a single factor is enough: there is no temperature offset and no material property involved, unlike conversions that cross between different quantities.
What is a millirad?
Millirads appear on older survey meters and in US regulatory limits.
What is a gray?
The gray is the SI unit of absorbed radiation dose: one joule of energy deposited per kilogram of matter.
Why does my answer differ from another converter?
Almost always because the other tool rounded the factor before multiplying. This page keeps full double precision through the calculation and rounds only for display, and it prints the factor it used so you can see where any difference came from.
Millirads to grays reference tables
| Millirads | Grays |
|---|---|
| 0.5 mrad | 5e-06 Gy |
| 1 mrad | 1e-05 Gy |
| 2 mrad | 2e-05 Gy |
| 3 mrad | 3e-05 Gy |
| 5 mrad | 5e-05 Gy |
| 10 mrad | 0.0001 Gy |
| 20 mrad | 0.0002 Gy |
| 25 mrad | 0.00025 Gy |
| 50 mrad | 0.0005 Gy |
| 75 mrad | 0.00075 Gy |
| 100 mrad | 0.001 Gy |
| 250 mrad | 0.0025 Gy |
| 500 mrad | 0.005 Gy |
| 1000 mrad | 0.01 Gy |
| 5000 mrad | 0.05 Gy |
Exact factor: 1 millirad = 1e-05 grays.
| Quantity | mrad | Gy |
|---|---|---|
| Dental X-ray | 0.5 mrad | 5e-06 Gy |
| Chest X-ray | 10 mrad | 0.0001 Gy |
| Head CT scan | 2000 mrad | 0.02 Gy |
| Radiotherapy fraction | 2e+05 mrad | 2 Gy |
| Full radiotherapy course | 6e+06 mrad | 60 Gy |
| Whole-body dose likely to be fatal | 5e+05 mrad | 5 Gy |
Published reference values, converted with the same factor this page uses.