I'm 5.5 and weigh 138. i usually wear a small to medium in dresses, depending on the style. For example, if I want my dress to be a little loose, I'll get a medium, but if I want it to be more flattering to my figure, I'll get a small. My bust is 40 inches, my waist is 32 inches, and my hips are 42 inches, and I purchased this dress in a size small. It fits perfectly! Not too big, but loose fitting, just like it should be. I hope this helps someone else determine what size they should purchase. It is also very good quality.