Oak Ridge Center for Risk Analysis collaborated with the National Cancer Institute to develop the Radiation Risk Assessment Tool (RadRAT). RadRAT is an online calculator for estimating the lifetime risk of cancer incidence for members of the U.S. population (or countries with similar cancer incidence rates) from exposure to ionizing radiation for doses below 1 Gy.

The calculator works using organ-specific dose estimates according to age at exposure and sex. Lifetime total cancer risk and organ-specific risk estimates are reported along with a 90% uncertainty range.
The reported lifetime risks are based on the risk models for the eleven cancers included in the 2006 report of the National Academies of Sciences' BEIR VII Committee and on the risk models for an additional eight cancers, developed by the NCI after the publication of the BEIR VII report.

RadRAT is accessible from the National Cancer Institute web site: http://irep.nci.nih.gov/radrat

Documentation for RadRAT has been published in the Journal of Radiological Protection: Berrington-Gonzalez A, Apostoaei AI, Veiga LH, Rajaraman P, Thomas BA, Hoffman FO, Gilbert E, Land C. 2012. RadRAT: a radiation risk assessment tool for lifetime cancer risk projection. J Radiol Prot. 32: 205-222. 

Estimating the Lifetime Risk of Developing Cancer from Exposure to Ionizing Radiation