to allow for growth? or some stretch? i mean thats why i buy pants or shoes slightly bigger than needed...:P ps im a guy

A simple search on google can reveal very graphic details about measuring bra size... here's the deal... there are two measures for bra size... one over the bust, and one under the bust. Add five inches to the under the bust measure, that gives you bra size. The difference in inches between the under the bust and over the bust measures indicates the cup size. According to the website (http://www.lingerie-feminineform.co.uk/), 80% of women wear the wrong size. re: why specifically 5"? This is not clearly explained anywhere, and in more reading, I see there are other rules about when 4", or 6" should be added to the under the bust measure, and when you should round the total down by one. This measure, by the way, is called the "band size". I believe the add 5" rule has to do with comfort and girth of the bra over the chest. The only place you want it to be tight is under the chest. You want 5" of "play" at the top of the bra to allow for comfort while you breathe and move around, pick up boxes, etc. If you measure your chest right under your arm pits, you will have a measure (in inches) that is very close to your bra size. I can only guess why the "under the armpits" measure is not used instead, it must have something to do with accuracy -- it's important that the bra be snug under the chest... so start measuring there. If it's any consolation -- I know somebody that's a pattern maker, she told me long agao that bra's and bikini tops are by far the most complicated patterns to design -- seems to me, somebody should overhaul this whole measuring thing -- if we can land a man on the moon, you'd think we could figure out an easier way to deterimine bra size. I'm sending her an email now... I will let you know here if she has any other insights.