I am having the same trouble, except I’m yet to have my BA (!) I’ve just lost weight and want to know my band size so I can buy the correct size Macom.
The results I found said measure under you bust and then add 4 or 5 depending on whether your measurement is odd or even – you would add 4 to your measurement making it 32″. As for your bust, I’ve read that for every inch difference between your under bust and bust measurement is a cup size, which would mean your cup size is E. 32C doesn’t sound like it’s right.
Some people swear by a Facebook page called Boob Or Bust but it calculated my bust size as 28E which made me laugh!!!
Good luck! Xx