Ok, immediate disclaimer: bra sizing is not a science. It is an art, and measurements can only give you a starting point. For example, my 28.5″ underbust and 40″ bust would suggest that I wear a 28HH, but that is usually too small now. Breast shape can heavily affect what size you need, and the best way to find the perfect bra size for you is to try on a whole bunch of bras until you find one that meets the criteria for a well fitting bra, is comfortable, and that you find attractive! A well fitting bra should make you feel good, first and foremost. If something is uncomfortable, regardless of what your measurements say you should wear, it isn’t right.
With all that said, this is generally the best way to find a starting point for your bra size:
1. Using a cloth tape measure, measure directly under your breasts. This measurement should be comfortably firm, on the exhale, but not incredibly tight. For this example, let’s say that you measure 31″.
2. Leaning forward slightly, so that all your breast tissue hangs forward, measure around the fullest part of your breasts. For most people this will be around the nipples. If you have pendulous breasts (a large difference between standing and leaning measurements), you may want to also take your standing bust measurement around the fullest part of your breasts and average these measurements together for the bust measurement. Let’s say that this measurement is 40″.
3. To calculate band size, use your raw underbust measurement, no inches added. If you are in between sizes (like our example, with 31″), you can either round up or down. Rounding down will ultimately provide the best support, but rounding up may be more comfortable, especially if you are making a large jump down in band sizes (ie: from 36 to 30). If you measure much closer to either band size, go with that one.
4. Subtract your band size from your bust measurement. Assuming that our imaginary bra sizing model decided to go with a 30 band, 40″-30″=10″. A 10″ difference is a UK GG cup. Below is how many inches correspond to each cup size.
1″ = A
2″ = B
3″ = C
4″ = D
5″ = DD
6″ = E
7″ = F
8″ = FF
9″ = G
10″ = GG
11″ = H
12″ = HH
13″ = J
14″ = JJ
15″ = K
16″ = KK
17″ = L
Now that you have a starting point for your size, you should try on this size and all the sizes around it, if possible. For our imaginary person who measured into a 30GG, she should try on 30GG, 30G, 30H, 32G, 32GG, 32FF, maybe even 28H, 28GG, 28HH. I understand that not all women (especially in the US!!!!!!!!!!!!!!) have access to a store that will carry these sizes, and may not be able to try on all these sizes. For them, while they’re getting their size nailed down, I would suggest buying from very inexpensive online shops (such as Brastop or eBay- make sure the eBay seller has a good return policy!!) and in large batches, planning on returning the sizes that did not fit well.
Once you have bras and you’re trying them on, how can you tell if they fit well? Use this criteria:
1. The band fits comfortably on the loosest hook, and you can pull it away from you ~1″-2″.
2. The center gore (the section that connects the cups in the front of a bra) lays flat.
3. No breast tissue is escaping from the front or sides AFTER SWOOPING AND SCOOPING. (Link leads to A Sophisticated Pair’s video on how to properly put on a bra. This is VERY IMPORTANT, and the video is probably NSFW due to women in bras haha.)
Obviously a bra can have other issues that indicate it is not a great fit, but these are the basic three to look for! If you have any questions, feel free to comment here or email me at firstname.lastname@example.org. There are also a few great online communities that you could ask for advice, including A Bra That Fits on Reddit and Bratabase.