Per the instructions, I ordered based off my waist size, which put me into a 2xl. It fit my waist well but was unexpectedly large in the bust. On the tightest lace I still had a huge gap there. I measured my bust and it's between a L and XL, so I would have been better off using those measurements instead. I am returning (since I bought this for an event that will be over before I could receive a replacement), but I recommend that new buyers don't go by waist alone as recommended - it is much, much looser in the bust than similar tops that I have bought before and does not cinch up nearly enough to make up for any difference. The thin ribbons that come with it are difficult to cinch up tightly and they feel weak and cheap, but do the job - if you need to size down for your bust then you may want to replace them so that you can compensate for the waist size difference if it's larger. The inside of the vest is very soft and comfortable, though, and I think this would have been a good top if I had a smaller size.