I ordered a medium size (5'11", 175 lbs, medium build) and this shirt fit perfectly. I've had sizing issues in the past, particularly with products made in Asia and made to Asian sizing standards, and going up in size is often a good idea, but it's always a bit of a gamble. However, with these garments, you can order your size without hesitation, knowing that it will fit you. No guesswork followed by frustration and sending it back (or settling for a size that doesn't quite fit like I've done in the past because I don't have to send it back). UPDATE // A few days later: This is also the first garment I've bought from Revain that hasn't COLLECTED after a wash!