Thats the problem, different makes seem to be different sizes. I get measured then try on one brand and am a cup size or something bigger or back size up. Its annoying. I never really worry about measuring anymore, but try on a range of cup sizes and go a size up or down back measurement wise until I find something that fits and supports.
Also as boobs fluctuate in size depending on the time of the month, I find that what fits one week is going to be a tight fit the next when period is due to arrive and you retain water. So I end up with varying sizes of bras for the month.
If you ask in store for someone to explain how a good bra needs to fit, you can probably work out from there when you try on for youself.
