It runs a little big (I'm 5'2'' at 103 pounds) and ordered an XS. It feels a little big but I do not care. The quality of this cotton is outstanding, not like other brands or similar shirts that you can get these days. I will definitely be ordering more.
I went with the Burlwood color. Love it!! I chose a size small, the fit is very comfortable. It is a relaxed fitting shirt, I will definitely have enough room for a t-shirt underneath also, without it looking to sloppy. The Carhartt logo on the sleeve is awesome. All around a great shirt.