Okay so I ordered this dress in a L and XL because I wasn't sure about which one would fit me. First off, the quality is AMAZING. It looks like it's worth way more than $40.... so it was a steal. I was wearing a bra (38C) and the L was snug. When I was zipped up it was tight, and it felt secure. I tried the L on without a bra and then it fit perfect. Because of the see through back and how tight the top zips up, my boobs stayed in place and didn't look bad when I wasn't wearing a bra. If it comes down to it, I may need to get some pasties because I don't know what it looks like in daylight outside (I wouldn't want anything to peek through). I am using this dress as a bridesmaids dress in a wedding. I tried on the XL with a bra and it was less tight that the L. With a bra on the XL wasn't super loose, but I liked how the L was tighter. I have hips and in the L and XL there wasn't a difference. The lace part on my dress sits a couple inches below my boobs... so it's flowy if you have a stomach and hips. It's just tight and fitting on the top. So base this dress off your CHEST size.
I ordered this after trying on one too many dresses for my quickie wedding. It was awesome! It flattered my 40G chest and hid any lumps and bumps with the flow of the dress. I am 5'9 and it pretty much hit the floor on me. I wear a 16/18 so don't be afraid of the sizing! I added a rhinestone belt and called it a day.
First off, I wear a size 18/20 shirt (44 bra) and size 24 pants (I know, total pear shape, and I usually have that huge gap in the back of my jeans too). So after I looked through ALL of the reviews I bought a 3X, just to be on the safe side (I usually wear a 2X, so I thought for sure it'd be too big), but sure enough it fits perfectly! It's a little long on me, I'm 5'6", but I can fix it/live with it. I hope my review helps you decided what size to get.