Oh gee I have no idea. My bra size is a 36 C and I'm squeezing and pushing to get though the head after that it's fine. It's not necessarily the stomach area that's the problem it's trying to get the damn thing on. If you are creative and a good wriggler bump your regular size up 2 sizes. I bumped mine up by 1 and it was still snug.

If you scroll to the bottom of the page of the item you are looking at there is a size converter to help you figure that out. But I usually go with an XL cause I am the same size but I am also tall.