I read a couple other reviews of different brands of coveralls and many said that sizing was a problem.  It wasn't with these.  I'm 5'8", weigh about 170, and have a 33-34 inch waist.  I ordered a medium and they fit just fine over jeans and a shirt.  The length is just a little long, an inch or two depending on the shoes, but no big deal.

I recommend these.  They're a lightweight polyester-cotton blend, have lots of pockets and adjustable waist tabs, and will work well during summer in the South if you have to wear coveralls.