Absorbed dose means the energy imparted by ionizing radiation per unit mass of irradiated material. The units of absorbed dose are the rad and the gray (Gy). The term “rad” (radiation absorbed dose) is the special unit of absorbed dose of 100 ergs per gram. Different materials that receive the same exposure may not absorb the same amount of energy. The rad is the basic unit of the absorbed dose of radiation (i.e., alpha, beta, gamma, and neutron) to the energy they impart in materials. The dose of one rad indicates the absorption of 100 ergs (an erg is a small but measurable amount of energy) per gram of absorbing material. To indicate the dose an individual receives in the unit rad, the word “rad” follows immediately after the magnitude, for example “50 rad”. One thousandth of a rad (millirad) is abbreviated “mrad”, and one millionth of a rad (microrad) is abbreviated “µrad”[1][2]


  1. IS Customs & Borders.
  2. Podgorsak, E. B., ed. (2005). Radiation Oncology Physics: A Handbook for Teachers and Students. Vienna: International Atomic Energy Agency. ISBN 92–0–107304–6. Retrieved 25 November 2012.