The standard size chair mat seemed large enough in theory but my chair kept rolling off the edge no matter how I adjusted the mat. This 48x60" mat is large enough for a navy pilot to land an F-18 on and both me and my carpet are happier.
This mat does not work well with medium pile carpet. Would probably work better on hard floor. My chair sinks into the mat making dents within just a couple minutes which prevents me being able to slide out from my desk - I have to lift my body and the chair to get it out of the dents. Really disappointing and frustrating. Would not recommend.