They measured me at 42D and it fit like a charm.
Help keep our community up to date! Now, I've always known that I had somewhat larger than average man-boobs, but they've never seemed comparable to the average ciswoman's in size. But basically, I do recommend going to get a professional fitting.
Bras strike me as largely unnecessary for us, since our larger frames splay things out so much we don't project enough to warrant heavy support.