I'm a size 32 and went with the medium. I like a true fit ant not too baggy so I can wear them under ski pants if needed. They are a little bigger than I expected for a medium but I don't mind, I think they're perfect - you can cinch the waist down if needed.
These pants rock, and the pockets are HUGE - you can even fit 40s in them.
If you need a pair of comfy pants you're at the right place.