Ok, being gay and male I don’t know anything about breast sizes. Ok, I guess some gay males might know more than I about bras, and ok, ok, some str8 guys would, too. Anyway, what does 34b mean? Is the number a measurement or just an index, like dress size 6.
I don’t know how they came up with them in the first place, but the number measurement refers to the band that goes around a woman’s torso, while the letter is the actual breast itself.
In the words of the Perfect Master What’s the world’s largest commercially available bra size (revisited)?
So, if a model says she is a 36c, that means her chest below the ribcage is 31 inches around and around the breasts she is 39 inches?
Nope. (How would she walk? That sounds rather unweildy.) Her chest below the rib cage indeed measures around 31 inches, but the C means that it’s three inches more than the actual around-the-chest size, not the band number, ie 34 inches.
But that’s not what the Straight Dope column quote says:
So a 31" ribcage measurement, plus 5, equals the 36 band measurement. To get a C, you need a nipple-level measurement 3 inches greater than the band, making it 39 inches.
Remember, we’re talking about an overall circumference measurement here - an extra 8" is significant but not gigantic.
From this interesting article.
One question of mine remains unanswered: in parts of the world that don’t use our alphabet (like, say, China, Japan, or Russia), how do they designate the cup sizes?
You say the ribcage is 31" then you add 5". What exactly is this measuring now?
Well, I can’t speak for China or Japan, but Russia, and other countries that use the Cyrillic alphabet would probably just use the Cyrillic equivalent, since it’s the same letters, just different “symbols”, if you follow?
Adding 5 inches gets a measurement that is one inch smaller than an A cup, so that determining cup size can be done simply by matching letter to number A=1; B=2, and so forth. That’s easier to remember than a=6; b=7.
In a practical sense, measurements don’t always tell which size will give the best fit. A woman whose measurements indicate a 34C, if she’s a small C cup, might be more comfortable in a 36B, or vice versa. Like any other piece of clothing, but even more so than most, getting a bra that fits well is often a process of trial and error.
34 B means you have a flat chested sister.
More or less, although as Kaitlyn explains, there’s some variance between a woman’s genuine measurements and which bra will actually fit her best. And remember, the bra sizing system goes in two-inch increments (although some manufacturers do make in-between sizes), so plenty of women are going to be an inch off from their bra size.
Then, of course, the style and cut of the bra makes a lot of difference too…
This is why women take so long in the fitting room!
An ill-fitting bra can lead to all sorts of problems, too. My shoulders can attest to that, if you care to interview them.
Another thing to note is that depending on the cut of the bra, you can go up a cup size and down a band size (or vice versa) and get the same fit.
For example. I’m a 40 DD. If I find a 42 D, that might fit, or a 38 E, or a 36 F, etc. This doesn’t work forever, (a 50 band size isn’t going to fit too well, no matter how small the cup is) but it does work within several sizes.
Bras are quite expensive for how long they last, so it’s important to find a good one and stick with it, especially if you’re large chested.
Meh. I’m a 34B and my breasts are delightfully hand-sized.
38D-ish reporting in. Bra sizes are just as stupid as other women’s clothing sizes. I’ve always understood that the number was your rib cage measurement, the letter was equivalent to the numbef of inches “off” your breasts actually measured at the largest point.
However, like every other item of clothing, I have bras in 4 different sizes that fit me. Depends on the stretchiness of the materials, the style of the bra, etc. So stupid! I wish I could buy stuff without trying it on and know it would fit!
Anyway, I’m the same size no matter what the tag on my clothes says, so I usually don’t give this much thought.
This thread needs pictures!! 
Be glad you’re not in Europe,where they measure in centimetres and you end up as a 85B or 90B
Bite your tongue. 34B is the one perfect size.
Kaitlyn: To celebrate us having the same bra size, I would totally suggest one of those jumping chest-bump things that men did (or maybe still do, but I think now it’s passé), but I’m a little sensitive right now.