Do not size up unless you are larger than a DDD'S. I'm 40DDD 198lb and I purchased a 3x and this one is loose at the top portion. Absolutely no boob support will definitely need a half bra if you are naturally larger (wink, wink 😉)you know who you are and what's the deal-E-O. I could get away with my regular size US 2x or size down to a 1x on this one. It's cute though. Runs slightly big due to having megga stretch. Looks just like the photos. Thin denim.