The sizing on this sleep shirt made me laugh out loud...I'm a medium to large (size 16) but I ordered a 3X for two reasons:  1) I don't like my night shirts to be tight, and 2) it's 100% cotton so I knew it would shrink.  I tried it on as soon as I got it, and let me tell you....*smile* it was tight before I washed it!  it's a 3X for very little people, LOL