I'm a 12/14 and i got a large and the dress fits nicely through the hips/seat. i'm kind of pear shaped so it's a bit large through the top, but i intend to layer another knit top under it so that's ok. 
 i didn't want the knit dress to be too tight or else it would stretch out after sitting. i like the colors and the fabric. the weave is loose and after snagging it on my glasses taking it off i'm careful with it. it will be nice into fall with a sweater.