For an age and a half I've been wearing a 36DD. I was pretty confident that was the right size. No riding up. No 4 boob profile etc. But I've lost weight and definitely boob mass. So I need a new bra.
My measurements are
30 under tight
31 under snug
37 round standing
40 round dangling (not pretty!!)
This works out at a 30G or 30GG depending on which site calc I use! 
Then a quick online shop makes me think that 30 band size are a little few and far between. Does that mean a 32FF would work?
(Not sure I can get my head around the large cup size yet)
TIA