I purchased a large to be on the safe side because I've put on weight. I'm 5'1 and 147lbs. The large fits well I could have also pulled off a medium if I wanted a more snug curve hugging night out fit and look. I purchased this for an everyday look to wear with flat tennis so I wanted it to fit tight but comfy also and sizing up allowed that. The dress is really cute and flattering. I would recommend.