About the Radiation Dose Converter
Radiation dose is reported in two different unit families - absorbed dose (gray and rad) and effective dose (sievert and rem) - and the numbers do not automatically match up unless the source and target units are the same type. This calculator converts a value between gray, rad, sievert, and rem so readings from different equipment, countries, or older records can be compared directly.
How It Works
Enter a dose value and choose the unit it is currently in along with the unit you want it converted to. The calculator converts your value to a common internal base figure and then divides that base by the target unit's factor to produce the converted result.
Formula & Methodology
To convert the default 1 sievert to rem: base = 1 x 1 = 1, then result = 1 / 0.01 = 100 rem. To convert 5 gray to rad: base = 5 x 1 = 5, then result = 5 / 0.01 = 500 rad. The same two-step process, multiply into a base, then divide into the target, applies to every combination of the four units.
Examples
Sievert to rem
Converting the default 1 sievert to rem returns 100 rem, reflecting the fixed 100-to-1 relationship between the two effective-dose units.
Gray to rad
Converting 5 gray to rad returns 500 rad, following the same 100-to-1 relationship that applies between the two absorbed-dose units.
Advantages
- Translates instantly between the SI units (gray, sievert) used internationally and the older units (rad, rem) still common in US medical and occupational records.
- Removes the need to remember that both scale relationships, Gy-to-rad and Sv-to-rem, use the same factor of 100.
- Handles absorbed and effective dose units side by side in one tool instead of requiring separate references for each.
Common Mistakes
- Treating gray and sievert, or rad and rem, as always interchangeable, when that equivalence only holds for photon and beta radiation, not alpha particles or neutrons.
- Misremembering the conversion factor as 1,000 instead of 100 when moving between SI and traditional units.
- Overlooking the difference between absorbed dose and effective dose entirely, and comparing a Gy reading directly against a Sv limit without checking which quantity each is meant to represent.
Edge Cases to Watch For
- This tool applies a radiation weighting factor of 1, so it treats Gy and Sv as numerically identical and rad and rem as numerically identical - accurate for X-rays, gamma rays, and beta particles, but not for alpha particles or neutrons, which carry higher biological weighting factors and need a different conversion in real dosimetry work.
- Absorbed dose (Gy/rad) measures physical energy deposited in tissue, while effective dose (Sv/rem) measures estimated biological risk; the two only line up numerically for radiation types with a weighting factor of 1, which this simple converter assumes throughout.
- Results display with up to six decimal places, so very small values such as microsievert-range doses still retain meaningful precision after conversion.
Common Use Cases
- Radiology and nuclear medicine staff reconciling dose readouts from equipment that reports in different unit systems.
- Occupational health and radiation safety officers reviewing dosimeter badge results recorded in rem against newer sievert-based limits.
- Students and instructors working through radiation physics problems that mix rad/rem and Gy/Sv units.