Due to the increasing interest in environmental protection against ionizing radiation on the international scene, the need for operational tools for radiological environmental risk assessment is becoming critical. Within this framework, this paper puts forward a fast and user-friendly computerized method to allow the transformation from exposure (expressed in Bq per unit of mass or volume) to dose (i.e., the energy deposited in the organism, expressed in Gy) received from any radionuclide by any non-human species, for a unit of time and a unit of “concentration” of radionuclide in the radiation source. The calculation principles used to determine this dose coefficient, expressed in Gy/unit of time per Bq/unit of volume or mass, are described for gamma, beta, and alpha radiation. Both internal and external exposure situations are considered. The domain of validity of the proposed model is specified, as is the way in which it has been computerized. The paper concludes by verifying the numerical accuracy of the tool and making initial comparisons between results from the described method and those developed at the European level.