This is the part that goes around your body. In a properly-fitting bra, it should be providing 90% of the support, which it does by being firm and level to the ground all around your body.
The Bridge (also known as the Gore or Centerpiece)
This is also a part of the band, but it's the small bit of fabric between the underwires that should be resting against your sternum.
This is the part that actually covers your breast. There are a few different types of cups:
- Quarter cup: this is the least coverage, often not even covering the nipple. cute, but not practical. this is a quarter cup.
- Demi cup: literally means 'half cup'. This is often the least coverage that can still be an every-day bra. The straps are often wider-set, and the bridge is often a bit higher than on a semi-demi bra. this is a demi-bra.
- Semi-demi (or three-quarter) cup: Most small-to-average bust styles are semi-demi bras.
- Plunge cup: The lowest bridge of the group.
- Full-coverage: there are a few different styles of full-coverage bras. A three-part cup has a panel going up the outside of your breast to narrow you. Minimizers will also be a full coverage cup. Basically, the name is self-explanatory. All or most of the breast is covered.
These are the bits going across your shoulders that connect the cup to the back of the band. They should only be providing 10% of the support of your bra. They are almost always adjustable by a little slider in the back.
Not always a part, but most “traditional” bras will have one. We usually only notice the wire when something is off in the sizing. The wire is there to provide separation, shape, and definition. Most non-wired bras will have a tendency to give a 'uniboob' look.
How Your Bra Should Fit
Your band should be at the same height front-to-back or slightly lower in the back than in the front. In that position, there should only be an inch or so of give on the loosest hook when the bra is new. The vast majority of women wear their band too big. When trying on a new bra, make sure to pull the band down on your back, then see if it still feels too tight. A few methods for estimating band size:
Measure: Measure firmly, with the tape-measure level, just underneath your bust. Lots of places will tell you to add 4 or 5 inches to this measurement. That is NOT CORRECT. Round up to the nearest even number, and try that band size. If that's too firm, try one size up from there. You should be one of those two band sizes, if you measured correctly.
You can also estimate from blouse size: a person who wears a 0-2 will often be a 30; a 4-6 will often be a 32; an 8-10 will often be a 34; a 12-14 will often be a 36; etc.
Judge by current bra size: if a new bra in the size you usually get has an inch of give on the tightest hook in that correct, low position (loosen the straps to get it down there!), go down one band size. If it has three inches of give, go down two band sizes. If it has five inches, try going down three band sizes.
If you have issues like:
- your straps are always falling down
- your straps are always digging
- your band is riding up above where it should be
- you're not getting as much lift as you would like
- you're popping out underneath the wire when you raise your arms
- your bra shifts throughout the day
Then go down a size or two in the band.
The cup should neatly contain all of your breast tissue. Take a look at where the wire is hitting you under your arm. Do you have anything spilling out under there? Do you pop out from the top of the cup, getting the terrible 'quad-boob' effect? When looking at your cup, do so while holding the band firm and in the correct position. Sometimes smaller-busted women keep going down in the cup because they don't fill out the larger cup size. The main thing to look for here is the positioning of the wire. It needs to be outside of all of your breast tissue.
Since we just changed your band size, you will need to change the cup size to compensate. A B-cup is not the same in every band size! Let's say you started out wearing a 36B that looks good in the cup when the band is low and firm. You usually wear a size 4 dress, and you measure 31" underneath your breasts. You would then want to try a 32 band. A 32B would be way too small! a 36B=34C=32D in total cup volume, so a 32D would be the first size to try on. For every band size you go down, you need to go up one cup size just to get the same amount of volume.
This gets tricky above a D-cup, depending on the brand. I'd recommend counting up the alphabet without worrying about double letters (European sizing), and then working out the equivalencies.
If you have issues like:
- you're popping out anywhere
- the wire digs into your sides
- you're not getting the correct amount of coverage for the bra-type you're wearing
- the bridge doesn't lay flat against your sternum
Then go up a cup size or so.
If you're having issues like:
- there's puckering or gapping in the cup (when the band is pulled tightly)
- the underwire is stabbing into your armpit
- the bra rubs the fronts of your shoulders
Then go down in the cup, or try a shallower cup-style.
Victoria's Secret cups often run deep. Look at how the wire is fitting you.
Sizes like 38C and 34AA are quite uncommon, when using the method I'm outlining here.
A minimizer will often make you look wider than a properly-fitted, seamed cup.
Lace and seams will be more supportive than contour (the foam-lined t-shirt bras).
You usually want to see your nipple-line be about halfway between the top of your shoulder and your elbow.
Not correct-fitting advice, but if you're looking for a ton of cleavage for date night, go down one cup size.
Adapted from a reddit post “Bras 101” by xanthochrome