Not very thick - so after a few hours of sitting the wheels of the chair create indentations in the mat thus making it more difficult to roll the chair - i'm average weight of 160 pounds too...
The chair mat works well in my computer room. It was shipped flat which worked for me. No unrolling and waiting for it to flatten out. I could use right away. Seems thick enough I have low pile carpeting and it stays in place. Had it for a few weeks- no cracks very light indents from chair roller legs. Just what I needed for home use.