Radio Spectrum Inventory Act of 2012 - Amends the Communications Act of 1934 to require the Federal Communications Commission (FCC), subject to specified national security, classified information, and public safety exceptions, and in consultation with the National Telecommunications and Information Administration (NTIA) and the Office of Science and Technology Policy, to: (1) biennially inventory each radio spectrum band from 300 megahertz to at least 6.5 gigahertz managed by each such agency, including information on the total spectrum authorized for each licensee or federal government user and the approximate number of deployed or authorized transmitters, end-user terminals, or receivers (excluding unintended radiators) in the band; and (2) make the information available to the public on a searchable Internet website.