I usually wear a small in shirts and ordered a small. Fits great. The length is a little short. Wish it were a tad longer. Hits right at the top of my low rise jeans.  I'm 5'8" 145 pounds for the record with a 34B chest size. Great fabric. Lightweight for work. The sleeves are shorter than I expected. More of a cap sleeve. Overall great uniform work shirt. May order a medium to get a little longer length.