I got the XL and the XXL.
The XL fit beautifully. I'm 5'3, weigh 200, and am a 38D.
The yellow dress came to just above my knees and was super comfortable.
I would suggest not wearing a dark colored bra or underwear, since it does show through the fabric, though the fabric isn't see-through! The fabric did bunch under my bust if I had been sitting but straightening the dress fixed that.

The XXL was too big, it fit me more like a bag.

Hope this helps!