Traditional methods for measurement of polarizing beamsplitter (PBS) parameters, especially the extinction ratio, require highly polarized light sources, alignment procedures, and/or experimental parameters that change over time, such as polarization rotations. In this work, a new method is presented that employs unpolarized light and a Faraday mirror. It is shown that precise extinction ratio and insertion loss values can be achieved in three single-sweep measurements without any alignment requirements or time-varying signals of any kind.