The USGS now offers a tool that accurately translates and interprets Landsat 8 OLI Quality Assessment (QA) bits, within the Landsat LDOPE Toolbelt.
Based on functionality developed by the Moderate Resolution Imaging Spectroradiometer (MODIS) Land Data Operational Product Evaluation (LDOPE) team at Goddard Space Flight Center, the Toolbelt can be downloaded as a zip file that contains the executables compiled for Linux 32-Bit, Linux 64-Bit, Windows 32-Bit, and Windows 64-Bit systems, accompanied by the source code and a readme file. Each command can be run directly by typing the executable name and its parameters from the tools directory. Details about the OLI QA Tool can be found at https://landsat.usgs.gov/l-ldope-toolbelt.

Source: USGS Landsat