I have the same medium sized shirt in navy blue that I bought from another department store and it fit perfectly. However this white shirt, at the same size from this seller, ran MUCH smaller. I can still wear it, but it's still a tight fit. Sizing is dependent on where it was manufactured. Most of the shirts from this seller are made in Jordan, the one that fits me well is made in Haiti. I bought another shirt in slate gray from Amazon in large, and that one was too big (also made in Jordan).