Cutting glass for a mirror only requires a glass cutter tool, a straight edge and the glass itself. Prices for glass cutting tools vary, and straight edges can be lumber, metal or any available surface that can withstand the sharp edge of aby tools used.
Individuals must wet the cutting wheel on the glass cutter tool for best results, applying even pressure as they cut along the glass, according to Instructables.com. The next step is to gently tap the glass on the front and back near the scored line. The glass should break evenly along the line, unless the initial scoring line did not have enough pressure applied.