I measure 31" round my ribs and 34" round my (pregnant) boobs. I'm currently wearing a 32B which still fits round the ribs but I'm overflowing out the top. According to the sizing charts on Next and M&S websites I should be a 36A, but surely that would be too big round the ribs?
Was fit by Bravissimo (who don't measure btw...they just look at your size/shaoe and try lots of bras on you in roughly the right size til they find the right fit) a few weeks ago and am a 34G (am also pregnant) - though admittedly I now have the bit round the ribs on the loosest setting.
Do not add inches onto the rib measurement ever.
I'd guess you're more like a 32D. When I was fit at Bravissimo they advised that cos I'm pregnant to get the bra to fit so the back fits on the tightest setting so you can expand it as your bump expands and have a the cup a little on the large size as they're likely to grow as pregnancy progresses.
I've never understood why bras are sized the way they are. Who thought of that? Why measure under the bust and then add four inches? Why? Why not measure under the bust, use that measurement and add inches for the cup size? I don't know why womens' sizing is so ridiculous. Why do we have to buy in 12, 14 or whatever when men can just buy by the ACTUAL measurement of their waist or chest. You would get a better fit then surely.
I don't understand either. like mrsmerryweather I'm an 8-10 (and would say the 8 mainly the top half!) and yet I often find that 32Bs cut into my ribs and - worse - leave protruding flabby bits at the side. So I go for the 34B and find it's just a little bit too big all over...sigh...