unit:REM

A Rem is a deprecated unit used to measure the biological effects of ionizing radiation. The rem is defined as equal to 0.01 sievert, which is the more commonly used unit outside of the United States. Equivalent dose, effective dose, and committed dose can all be measured in units of rem. These quantities are products of the absorbed dose in rads and weighting factors. These factors must be selected for each exposure situation; there is no universally applicable conversion constant from rad to rem. A rem is a large dose of radiation, so the millirem (mrem), which is one thousandth of a rem, is often used for the dosages commonly encountered, such as the amount of radiation received from medical x-rays and background sources.