Radiation dose converter
Pick the quantity, type a dose and choose the units. Absorbed dose (gray, rad) and equivalent dose (sievert, rem) are different quantities, so each has its own set of units. Gray cannot be converted to sievert here, because that needs radiation weighting factors.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Choose absorbed dose (Gy, rad) or equivalent dose (Sv, rem).
- Type the dose, then choose the unit you have and the unit you need.
- The result is shown with its unit, along with the same dose in the SI unit.
Conversion factors
| Quantity |
Relation |
| Absorbed dose |
1 rad = 0.01 Gy, so 1 Gy = 100 rad |
| Equivalent dose |
1 rem = 0.01 Sv, so 1 Sv = 100 rem |
| Prefixes |
1 mGy = 0.001 Gy, 1 μGy = 10⁻⁶ Gy (same for Sv) |
Worked example
A dose limit of 5 rem per year equals 5 × 0.01 = 0.05 Sv = 50 mSv. A reading of 100 mrad is 1 mGy, or 1,000 μGy.
Tips
- Gray and rad measure energy absorbed per mass; sievert and rem add the biological weighting. Never read one as the other without knowing the weighting factor.
- Check whether a number is per hour (a dose rate) or a total dose; this tool converts the unit only and keeps any “per hour” in your head.
Frequently asked questions
How many rad is 1 gray?
1 Gy = 100 rad, because 1 rad is defined as 0.01 Gy. Both measure absorbed energy per unit mass; the gray is 1 joule per kilogram.
How many millisieverts is 1 rem?
1 rem = 0.01 Sv = 10 mSv. So 100 mrem is 1 mSv, which is the way many dose limits and readings are quoted in the US versus elsewhere.
Why can't I convert gray to sievert?
Sievert is the absorbed dose multiplied by weighting factors for the type of radiation and, for effective dose, for the tissues exposed. The factor depends on the situation, so there is no single conversion. For X-rays and gamma rays the radiation weighting factor is 1, but that is a decision for you to make, not a built-in assumption.
Is a rem the same as a rad?
No. They have the same numeric size only in the special case of a radiation weighting factor of 1, but a rad is absorbed dose and a rem is equivalent dose. Convert rad to Gy and rem to Sv separately.