All right, this is a really important and also potentially life changing step. To start with, it is important that you know that everything they tell you about your bra size at shops like Victoria’s Secret and Bra’s n Things is a complete lie. Seriously. People wearing the wrong bra size is such a big problem that over 80%* of women are doing it. The most common mistake made is having a band at least 1 size too big and cups at least 1 size too small. This happens because women generally have no idea how bra fitting works because a large proportion of the stores we buy from use something called the “+5 method” when sizing us for a bra.
The Wrong Method
The +5 method means that you measure your underbust, add 5 inches to it, then measure your bust, and subtract the bust from the underbust to get the cup size (1 inch difference A cup, 2 inch difference B cup, and so on). So using the +5 method, if you have a 28 inch underbust and 37 inch bust, they will: 28+ 5= 32, 37-32= 5, A1 B2 C3 D4 DD5, put you in a 32DD. This is the wrong sized bra, and is likely to leave you with a too big band which rides up or down your back, the bra smooshing your breasts and not sitting properly flush against your chest, and you’ll likely be wearing the straps really tight to compensate for the lack of support. The +5 step was used back when bras were made of extremely rigid material with no extra stretch, whereas today’s bras are basically all made of material with some give, making it totally redundant and in fact harmful.
The Proper Method
So, the real way to size bras, sometimes called the +0 method, is just that simple – cut out that ridiculous +5 step. So using our previous example of a woman with a 28 underbust and a 37 bust, 37-28=9, A1, B2, C3, D4, DD5, E6, F7, FF8, G9= This lady would be a 28G. Yes, that’s right, a 28G. This, while on the larger side, is not at all an uncommon size when people are sized correctly. I can assure you that if these are your measurements the +0 method has immeasurably more comfortable results than the +5 method because I wear a 28G (I used to wear a 34C – ouch!).
Now, because I wear a size that bra manufacturers around where I live like to think are obscure, I have to order my bras online, which is a real pain because I don’t get to check for other non size related fit issues and have to rely on reviews by others. Now, if you have found you are a hard to find size, say a 30D, and you don’t have the money to go online just yet, fear not. You can still probably improve on where you are now.
How Cup Sizing Works
Not all Cs DDs and Gs (and beyond) are built the same. A 32C is 3 sizes smaller in volume than a 38C, and has the same cup volume as a 34B. This is because your cup size is all about the proportion of your breasts to your body/underbust, nothing more. So say you are currently wearing a 34A but have measured yourself as a 30D, but you can only find D cups down to a 32D. In this case, you should try a 32C. The band may still be loose and cause fit issues, but the cups will fit much better as the 34A was one cup size too small for you. This is using a method known as sister sizing. Basically, once you find your bra size, (say my 28G), you can go up in band size and down in cup size to find other bras with your cup volume. People do this for all sorts of reasons – not enough money to ship overseas, some bras are tighter or looser in the band and are more comfortable in a size up or down in band, or sometimes people measure as one size but feel more comfortable a band size up or down. Here’s a great blog post with more to say on the matter: http://fullerfigurefullerbust.com/2012/08/16/bra-sizes-do-not-exist-without-back-sizes/.
If this post has information that is new to you, I seriously absolutely totally recommend that you check out this subreddit: http://www.reddit.com/r/abrathatfits. It’s a totally welcoming environment that tolerates no creepiness and has a lot of FAQ information in the side bar. I’ll leave you with just one lat piece f advice – be prepared to be shocked by your new bra size. I absolutely rejected that I was bigger than a C cup at first. I wore a 32DD at first, shocked that it fit better, and then realised I still had a lot of fit issues. It took me a lot of time to accept that I was a 28 band. So, even if this stuff scares you a bit or seems like a bunch of nonsense, please just give it a chance. Your body will thank you for it.
Statistic taken from *http://www.quixotegroup.com/clients/documents/newfitstudypressreleasefinal.pdf