I usually wear large so I just went with my usual for this dress. I wear sizes 10-12, sometimes even a 14 depending on the brand, and I am 5'6" and an hourglass shape. The shape was way too baggy around the hips and my figure was completely lost, so I'm returning it and ordering a medium. Size issue aside, this dress is great! Very comfortable and cute. It is lined, and both the liner and the dress are a nice spring/summer material. I hope the medium works because I really want this dress to work out!