Radiation Dose Converter

Radiation dose is the amount of ionizing radiation energy absorbed by matter. Two main quantities exist: absorbed dose (gray or rad), which measures energy per unit mass, and dose equivalent (sievert or rem), which accounts for biological effect on human tissue. The sievert (Sv) is the SI unit of dose equivalent, equal to a gray multiplied by a quality factor.

The gray (Gy) measures absorbed dose: energy per unit mass (joules per kilogram). The sievert (Sv) measures dose equivalent: absorbed dose multiplied by a quality factor that depends on the type of radiation. For photons and beta radiation, the quality factor is 1, so 1 Gy = 1 Sv. For alpha particles and neutrons, the quality factor is higher, so the same gray produces more sieverts.

The rem (roentgen equivalent man) is an older unit of dose equivalent used primarily in the United States. One sievert equals 100 rem. The millirem (mrem), one-thousandth of a rem, equals 0.00001 sievert. Many historical occupational and medical records use rem or mrem.

The rad (radiation absorbed dose) is an older CGS unit of absorbed dose, equal to 0.01 gray. It is the absorbed-dose equivalent of the rem. One gray equals 100 rad. Though mostly superseded by the gray, the rad still appears in older literature and some specialized contexts.

This calculator is for informational reference only. Radiation dose calculations for medical, occupational, environmental, or health purposes must be performed by qualified professionals using verified methods and equipment. Consult a medical physicist, health physicist, or qualified occupational health specialist for any application involving human exposure.