Writing about breast size

[SeriousBrainDamage]

I give up.

 

[SeriousBrainDamage]

Turns out, I'm not very good at giving up.

It also turns out I may have been wrong all along.
Apparently the bra sizing is more complex and less intuitive of what I imagined.

That said, I refuse to yield completely.
Cup size is still, in my opinion, a quick(lazy?) way to describe the relative size of breast.
A girl with a D cup will always have medium to large breasts, compared to her figure.
If she's lean and petite , they'd be smaller, if she's tall and big, they'd be bigger too.

I know, this is kind the other way around of what I did write previously, but I think it still holds a value.

 

[insertnamehere]

A girl with a D cup will always have medium to large breasts, compared to her figure.

That's a decent perspective, then. I think the difference still scales; that is, a 28D will still be somewhat smaller 'compared to her figure' than a 36D, but worrying about that is probably pendantic. It can be rather difficult to work out what a particular bra size really means, without an army of chest-diverse women willing to be examined, so I tend to avoid mentioning sizes entirely.

 

[gene.sis]

A girl with a D cup will always have medium to large breasts, compared to her figure.

I think the difference still scales; that is, a 28D will still be somewhat smaller 'compared to her figure' than a 36D

It's rather the other way around...

Assuming perfect fit, D cups would look bigger on a 28" frame than on a 36" frame.


To simplify things, imagine the chest as a rectangle.
The cup size is the difference between underbust circumference and the bust circumference.
Now the cups would protrude about half of the difference. (This isn't exactly true in reality as the breasts and bodies aren't rectangles... but you can round that model later.)
A is 2"
B is 2.5"
C is 3"
D is 3.5"

For the rectangular chest, the band size is the sum of all four sides.
Assuming a width-depth ratio of 2:1 for the chest, we get a chest depth of
4.6" for band size 28
6" for band size 36

and a chest width of
9.3" for band size 28
12" for band size 36

Half of that is the width of a single bosom:
4.6" for band size 28
6" for band size 36

Both of them would protrude 3.5"
In percent, this means:
76% for band size 28
58% for band size 36
(the same applies to the ratio of width and protrusion)

So the rectangular 28D would look about 30% bigger than the 36D compared to the figure.


For non-rectangular women and their breasts, the numbers are different but you get the idea.

As non-rectangular breasts have a more rounded shape, they won't grow only forward but also outwards.
If you take the basis width of a single bosom of 28D in the above model, it says 4.6".
This wouldn't be enough for a hemispherical cup that would have a sphere diameter of 7".
So the breasts might be pushed outwards (this comes with less protrusion) while still forming a cleavage.

For 36D it would be 6" and 7".

So in this adjusted model, the 28D would protrude more to the sides than a 36D (compared to the figure)


You could surely refine the above and use actual data instead of estimations.
This would lead to a more accurate but I guess this is enough to get the idea.

 

[insertnamehere]

You're right, the numbers check out. I was thinking too absolutely.

 

[SeriousBrainDamage]

Whew...
I'm not one for Math myself, that has probably something to do with the fact that I write erotica fiction in my spare time instead of calculating matrixes, and I kind of expected to find like minded individuals here, but alas..

So the rectangular 28D would look about 30% bigger than the 36D compared to the figure.

Before my last post, I was under the impression that, when considering breast size, the cup size was a fixed value.
So when taking into account the whole chest, you had the torso circumference(the band size) + x, where x is a specific cup size, and this value stayed the same regardless of the band size.
That lead me to think, that the actual breasts size was indipendent, measure-wise, from everything else and that it was something that had a precise descriptive value.

That is not the case, to my understanding.

Instead it works something like this: to a specific band size, let's say 32, which is considered the average, you have a specific cup size, let's say C, which again is considered average; if you pic a larger band (or smaller) the default cup size will still be C.
This C value changes from country to country, but there are just a handful of accepted different system out there.
Of course, there will be a difference in the sheer volume of the cup of a 32C and a 36C, but to my understanding the proportion can be safely considered linear.( that's for you who like math so much )
That means, if woman needs a D cup, her breast will always be fuller in respect to her figure(specifically the torso size); and if she needs a B cup, her breast will always be less prominent, despite the band size chosen.

This way of thinking is an approximation, I hope an understandable one, that takes into account only well proportioned body (most of the time it's what I like to describe).
Deviation from the mean can be handled with specific descriptions of the body shape.
Again, paticular breast shapes can and should be handled with a separate description.
That's all the information I need to write.

That is to say, that despite the apprenly unneded complexity of the matter, rounding the numbers and simplifying a bit, there is still a way to use this information, that is use the convened meaning for breast cup's sizes.
That band size is trickier to use, because it directly overlaps with bodily descriptions.
A thin girl can't have a 38DD, can she?
I mean yeah, possibly, but she would be some kind of freak of nature.
But if you just state she has D cup breast, it just works: are they 28D? 30?
I don't know, I don't care, because I get the idea.

That's all that matters to me.

Now, know this, under no circumstances you lot will be able to goad me into another argument like this one. Ever!

 

[Sune's Kiss]

I honestly don't like fruit, sports balls, etc. very much. Though, I don't like bra sizes either.

I've seen it done, and it doesn't sound right, to me.

But, that could just be me.

I try to find other ways to fit it in - flat, modest, large, bouncy, aging, youthful, perky, torpedo, and other adjectives to make up an overall feeling for breast size and weight.

If there's major breast expansion going on - describe them in relation to the size of the female. Or other observers.

Have someone marvel that they can't get their hands around them, have them get in her way or watch them grow until they are too massive to walk properly, and our poor girl can't reach past them with her arms.

Yes, my advice would be to avoid the clinical and embrace the descriptive.

The great thing about this medium is that it calls upon the readers imagination. If you write about the hero brushing his hands across the rock-hard nipples of a maiden's pert breast, they're not going to be thinking "Is it an A cup or a C cup?", they're going to think about how those erect little nubbins would feel against their palm. Sometimes being vague and letting the reader fill in the blanks is better than "She had precisely 15cm of cleavage, no more, no less."

 

[gene.sis]

I'm not one for Math myself, that has probably something to do with the fact that I write erotica fiction in my spare time instead of calculating matrixes, and I kind of expected to find like minded individuals here, but alas..

Well... imagine there are two guys who are going to push their dicks into one pussy at the same time. I think it's rather important to be able to calculate if they both fit inside BEFORE they rip that poor girl's pussy apart!

That is not the case, to my understanding.

Yes.

Instead it works something like this: to a specific band size, let's say 32, which is considered the average, you have a specific cup size, let's say C, which again is considered average; if you pic a larger band (or smaller) the default cup size will still be C.
This C value changes from country to country, but there are just a handful of accepted different system out there.

Systems are slightly different. Though to understand what is going on, you should stick to one system to avoid another dimension.

Of course, there will be a difference in the sheer volume of the cup of a 32C and a 36C, but to my understanding the proportion can be safely considered linear.

Well, no exactly linear.
Both "protrude" about the same amount. (This is not exactly true because there is an angle/radius going around the cup.)
36C has more base width for the cup, so the relation of the protrusion to the base width will be lower.
So 36C would look slightly smaller compared to the figure than 32C

That means, if woman needs a D cup, her breast will always be fuller in respect to her figure(specifically the torso size); and if she needs a B cup, her breast will always be less prominent, despite the band size chosen.

Well, for the same band size, D is bigger than C. C is bigger than B...
For the same band size, this is always true.

But...
A girl with a "perfect fit" of 32C could also wear 30D or 34B.
That doesn't change her breasts.

That is to say, that despite the apprenly unneded complexity of the matter, rounding the numbers and simplifying a bit, there is still a way to use this information, that is use the convened meaning for breast cup's sizes.

Well, as nobody can properly decode the information, there is not much actual meaning behind it except the anecdotal one.

A thin girl can't have a 38DD, can she?

Well, it might be possible if her body shape is hourglass or inverted triangle.
Also depends on the height.

But if you just state she has D cup breast, it just works: are they 28D? 30?
I don't know, I don't care, because I get the idea.

Again, it's rather anecdotal.

Let's consider a small, slim girl and a tall, slim girl.
Both have the same proportions, so if you look at them from the right distances, they will both look the same. (As they are roughly proportional.)
Now let's say they both have breasts that perfectly fit into D-cups...
The small girl's breasts will look huge while the tall girl's breasts will look rather average.
So while the proportions of the bodies are the same, the proportions of the breasts are quite different.


The "problem" with cup sizes is that they only serve as a way to standardize fabrication and help women to get a starting point when searching for a bra.
There was never a need for consistency of any kind.


So, besides the anecdotal value in dialogs and looking at blurbs, I — personally — wouldn't consider using it.

 

[Sune's Kiss]

Yeah, I'm still not convinced that using bra size is the way to go.

If you want to write about your protagonist grinning like an idiot after finding lacy 36C bra hanging off the lampshade in their bedroom, then reminiscing about the creature of pure femininity that left it there in her haste to get to work in the morning, then have at it.

Using it to describe the woman beneath the bra...? Not so much.

 

[SeriousBrainDamage]

Well... imagine there are two guys who are going to push their dicks into one pussy at the same time. I think it's rather important to be able to calculate if they both fit inside BEFORE they rip that poor girl's pussy apart!

Well, that's exactly how far my math goes

Well, no exactly linear.
Both "protrude" about the same amount. (This is not exactly true because there is an angle/radius going around the cup.)
36C has more base width for the cup, so the relation of the protrusion to the base width will be lower.
So 36C would look slightly smaller compared to the figure than 32C

I think I have made it clear enough mine was an approximation.
Good enough to understand and make understand, not very useful if you're gonna buy your gf a bra though.

But...
A girl with a "perfect fit" of 32C could also wear 30D or 34B.
That doesn't change her breasts.

That's because of cross sizes, it doesn't really mean the cup is the same between a 30D and 34B.
A woman could wear also those, but that's just because the aggreagated measure of band+cup is almost the same.
Her perfect fit, as you say, will still be a 32C.
When she wears a 30D the cup will be loose and the band tight, with a 34B it will be the other way around.

To paraphrase you, this doesn't change my point.

Well, as nobody can properly decode the information, there is not much actual meaning behind it except the anecdotal one.

Anedoctal has nothing to do with the meaning of convened, it's quite the opposite in fact.
It's clear we do not agree on this point.

Again, it's rather anecdotal.

Let's consider a small, slim girl and a tall, slim girl.
Both have the same proportions, so if you look at them from the right distances, they will both look the same. (As they are roughly proportional.)
Now let's say they both have breasts that perfectly fit into D-cups...
The small girl's breasts will look huge while the tall girl's breasts will look rather average.
So while the proportions of the bodies are the same, the proportions of the breasts are quite different.

I'm not entirely sure you use the word correctly, but I digress..

Being tall and being slim are two different qualities.
A tall girl, to be also slim, has to have chest, waist, and hips measurments, that respect a given ratio.
This ratio is the same for a small girl, or she wouldn't be slim by definition.
The tall girl(5.10> ?) will have a, say like 36D?
The small girl (5.2< ?)will have then a 32D?
Same proportion.

I higlighted that sentence because I'm not sure what you mean.
I thought we did agree that D cup is not a fixed volume, is it?

That is not the case, to my understanding.

Yes.

The "problem" with cup sizes is that they only serve as a way to standardize fabrication and help women to get a starting point when searching for a bra.
There was never a need for consistency of any kind.

That may have been the original intended purpose, thought it would be silly if the whole measurement system didn't have some kind of consistency, wouldn't it?
Or maybe you mean consitency between different countries?

What's sure is that it would fail it's purpose if it didn't manage to frame women's breast sizes with a sufficient degree of accuracy, don't you think?
And by the way, purpose and use often but not always line up.

 

[gene.sis]

That's because of cross sizes, it doesn't really mean the cup is the same between a 30D and 34B.

Actually... it is.
A underwire size of 34 is used for 36A, 34B, 32C, 30D, 28E
And the underwire size is the basis of the cup, though the actual position of the cup might differ depending on the band size.
(But even though they are roughly the same size, they will still look different due to the width of the chest.)

Anedoctal has nothing to do with the meaning of convened, it's quite the opposite in fact.
It's clear we do not agree on this point.

What I wanted to express is...

If you see a woman, can you tell her cup size?
If so... how do you know? How did you learn it?

Being tall and being slim are two different qualities.
A tall girl, to be also slim, has to have chest, waist, and hips measurments, that respect a given ratio.
This ratio is the same for a small girl, or she wouldn't be slim by definition.

Yes, exactly.

The tall girl(5.10> ?) will have a, say like 36D?
The small girl (5.2< ?)will have then a 32D?
Same proportion.

Yes, the bodies in this example might have the same proportions. (If we assume a ratio of 2:1 of chest width and chest depth)

I higlighted that sentence because I'm not sure what you mean.
I thought we did agree that D cup is not a fixed volume, is it?

Yes, D cup is not a fixed volume.

The thing was to assume that they have a proportional body. So if you assume both have no breasts and you would look at them from a proportional distance, they would look exactly the same.

Now, putting (perfect-fit) D cups on both of them would result in a different look.

So the same cup doesn't result in the same volume, nor does it result in the same look.

That may have been the original intended purpose, thought it would be silly if the whole measurement system didn't have some kind of consistency, wouldn't it?
Or maybe you mean consitency between different countries?

Well, the measuring system itself is consistent. (I guess I worded it badly.)
(Though the different countries' systems actually aren't consistent.)

What I wanted to say is that a bra size system doesn't need to make any sense in terms of look or volume.

It only has to make sense for manufacturing and fitting.
Using/creating a system that makes sense in terms of looks would only confuse the manufacturers. (Basically in the same way as the bra size system confuses anyone who thinks it conveys a certain look, volume, or both.)

What's sure is that it would fail it's purpose if it didn't manage to frame women's breast sizes with a sufficient degree of accuracy, don't you think?

No, because the purpose is to accurately describe the measurements of a bra.


If you want something that at least roughly describes the look (perceived size) of the breasts (proportional to the body), you could use a system that does exactly this.

 

[SeriousBrainDamage]

Actually... it is.
A underwire size of 34 is used for 36A, 34B, 32C, 30D, 28E
And the underwire size is the basis of the cup, though the actual position of the cup might differ depending on the band size.
(But even though they are roughly the same size, they will still look different due to the width of the chest.)

This is getting too techical.
I'm more interested into a more global measure of the breast.
And yes, if you're wondering the pun was totally intended.

What I wanted to express is...

If you see a woman, can you tell her cup size?
If so... how do you know? How did you learn it?

You wanna know how many times did I get it right just by looking?
I didn't take notes to be honest.
Jokes aside, I cannot answer to that, because I really don't wonder about a girl breast size when I look at her.
You could say I mentally divide breasts like:

n/a, small, fair, big, very big, fat ass grandma.

Substitute that with a letter and you have your cup sizes.
But that's not something I rationally process when I meet someone.
How did I learn the correlation?
Same way I did learn many other things: patter recognition, direct experience, reading, confrontation with my peers.

Now, putting (perfect-fit) D cups on both of them would result in a different look.

So the same cup doesn't result in the same volume, nor does it result in the same look.

I'm not persuaded by that.
But it is surely something that needs more testing on my part. Extensive testing, I may add.
I'll fill you in once I get the results.

What I wanted to say is that a bra size system doesn't need to make any sense in terms of look or volume.

It only has to make sense for manufacturing and fitting.
Using/creating a system that makes sense in terms of looks would only confuse the manufacturers. (Basically in the same way as the bra size system confuses anyone who thinks it conveys a certain look, volume, or both.)

If you want something that at least roughly describes the look (perceived size) of the breasts (proportional to the body), you could use a system that does exactly this.

A measure system is a way to quantize or quantify something that exists in nature.
Its intrinsic feature is to be more rigid than the nature it tries to describe.
Of course the measure system we're considering is that of bras, not of a breasts, so there's one additional step.

Numbers>Tissues>Breasts

instead of

Numbers>Breasts

Let's consider the hypotesis of having a system just like that, one to measure directly breasts.
It would have numbers from one to ten and an index of firmess, like abc or with greeks so we don't get confused.
Let's leave aside shapes and angles.
The system would be made by expert boobologists of course, after long an extensive direct measurment of countless of female volunteers.

How would the average joe, the man on the street, correlate such finely tuned measurement system with first hand experience?
Patter recognition, direct experience, reading, confrontation with his peers.
It's not like he would go around with a little caliber and a tape measure groping girls to build his own reference.

What I ask you is: is that so much different than what we have now?

And I raise by asking you: is that so much different than dividing breasts in:

n/a, small, fair, big, very big, fat ass grandma ?

How much do we convene on the meaning of small breast ?
Can you quantify that?
Are small,big, etc.., just better beacause they are inherently more vague?
I'm not sure they are, because my hand is not a caliber whichever is the case.

 

[Spindizzy]

The problem is cup size is also not an objective measure. It varies a lot by style, by manufacturer and by country.

Worse, readers perception of what the different sizes mean if often flawed. For example if you were to mention a woman's D cup breasts you would broadly speaking be talking about a woman with an average sized bust but many of your readers are going to assume that D cups means she's noticeably larger than average in the chest department.

Maybe one day the fashion houses of the world will present us a truly objective system of sizes and measurements for women's clothing (and also usable pockets) but until that day comes simply saying "she's a C cup" or "size 6" is as likely to confuse readers as inform them

 

[insertnamehere]

I'm more interested into a more global measure of the breast.

There is none. This is true for both bras and breasts, if you care about the distinction.

n/a, small, fair, big, very big, fat ass grandma.

Substitute that with a letter and you have your cup sizes.

And which cup size do you associate with each of those descriptors?

How did I learn the correlation?
Same way I did learn many other things: patter recognition, direct experience, reading, confrontation with my peers.

Then you learnt wrong. Or, more specifically, because your current beliefs are inaccurate, you're still in the process of learning.

I understand you've gone through most of your life with the impression that cup sizes have some correlation with actual breast size, apparent or otherwise. Whether your perception is correct or not, it is shaped by your personal experiences. Since none of your readers have undergone your own life experiences, they will tend to have signficantly different perceptions of cup size. It is your responsibility, as a writer, to communicate your ideas in a way that the reader can interpret; therefore, cup sizes in isolation are useless.

 

[SeriousBrainDamage]

Well, I was trying to lighten the mood of a conversation which I felt it was getting too tedious.
Seems like I missed the spot.

Then you learnt wrong.

It may be, of course.

Or, more specifically, because your current beliefs are inaccurate, you're still in the process of learning.

Aren't we all?

And which cup size do you associate with each of those descriptors?

Do you really care?

I understand you've gone through most of your life with the impression that cup sizes have some correlation with actual breast size, apparent or otherwise.

That's something I didn't really give much thought before this quarrel, honestly.

Whether your perception is correct or not, it is shaped by your personal experiences. Since none of your readers have undergone your own life experiences, they will tend to have signficantly different perceptions of cup size.

That's tricky. How do you know about that? Couldn't it be said about almost everything else I, or you for the matter, write?

It is your responsibility, as a writer, to communicate your ideas in a way that the reader can interpret; therefore, cup sizes in isolation are useless.

Resposibility? That's not the word I would use.
I'd say it should be my goal.
And it is, don't you worry

Worse, readers perception of what the different sizes mean if often flawed. For example if you were to mention a woman's D cup breasts you would broadly speaking be talking about a woman with an average sized bust but many of your readers are going to assume that D cups means she's noticeably larger than average in the chest department.

And why is that? Are you referring to audiences from different countries? Are you considering a specific widespread flaw in perception of breast size-cup size correlation? Care to share it with us?
Or maybe that is just a guess, to reinforce your point?

Guys, you're all so adamant on this. It just irks me, honestly.
I played the herald of doubt, the Devil's advocate, so to say.
Keep at it, don't really know what else to say

 

[insertnamehere]

Do you really care?

Yes, but only because you would then be forced to say something like, "I consider D-cups to be large," to which I could then respond, "Well, the average bra size in the US is between a 34D and a 34DD, so your perception of cup sizes must be inaccurate." Since cup sizes are not tied to breast size, I could say something along those lines no matter how you respond, but I require an example from the horse's mouth, so to speak.

Couldn't it be said about almost everything else I, or you for the matter, you write?

This is an unfortunate reality of writing. If you say someone is 'tall', well, what does that mean, exactly? We rely on common understandings of the definitions of words, not on the imaginary cut-off point for being tall. It doesn't matter what height the reader envisions, because the point is, the character is tall.

Referencing X-cup breasts does not have this same effect, because cup sizes aren't defined as actual breast sizes. You're left with that imaginary cut-off point.

Guys, you're all so adamant on this. It just irks me, honestly.
I played the herald of doubt, the Devil's advocate, so to say.
Keep at it, don't really know what else to say

Hey, if you stop responding, this thread will probably die. (But please don't do that.)

 

[gene.sis]

But it is surely something that needs more testing on my part. Extensive testing, I may add.
I'll fill you in once I get the results.

Manual testing, I assume ^^

Let's consider the hypotesis of having a system just like that, one to measure directly breasts.
It would have numbers from one to ten and an index of firmess, like abc or with greeks so we don't get confused.
Let's leave aside shapes and angles.
The system would be made by expert boobologists of course, after long an extensive direct measurment of countless of female volunteers.

How would the average joe, the man on the street, correlate such finely tuned measurement system with first hand experience?
Patter recognition, direct experience, reading, confrontation with his peers.
It's not like he would go around with a little caliber and a tape measure groping girls to build his own reference.

Well, if you would want a system that roughly describes the optical size of breasts, I'd go for two basic numbers...
- BTCR (breast width to chest width ratio.) You would add the width of the broadest part of each breast, multiply it with 100 and divide that result by the chest width. If the number is 50, the breasts would be rather tiny. If the number is 100, they would cover the full front. If it is above 100, you would even be able to see the breasts on both sides if you look at the woman from behind.
- PF (protrusion factor.) This would describe how much the breasts protrude in comparison to the BTCR. It indirectly gives a clue about the horizontal roundness of the breasts. A number of 5 would mean that the breasts are hemispheres. A number below 5 would mean that they are flatter. A number 5 would mean that they are protruding so much that the radius center of the breasts is even in front of the chest base. 10 would mean that they are basically globes glued to the chest (extreme fake tits)

Then, you might want to have additional values for sagging, pointing, and nipple position.

How would the average joe, the man on the street, correlate such finely tuned measurement system with first hand experience?
Patter recognition, direct experience, reading, confrontation with his peers.
It's not like he would go around with a little caliber and a tape measure groping girls to build his own reference.

What I ask you, is that so much different than what we have now?

Well, with the 2 numbers mentioned above, you could actually estimate the optical size of breasts without any measuring.

So it would definitely make a difference. (But as I don't like numerical descriptions in stories, I wouldn't use it anyway.)

You wanna know how many times did I get it right just by looking?
I didn't take notes to be honest.
Jokes aside, I cannot answer to that, because I really don't wonder about a girl breast size when I look at her.
You could say I mentally divide breasts like:

n/a, small, fair, big, very big, fat ass grandma.

Substitute that with a letter and you have your cup sizes.

But that's not something I rationally process when I meet someone.
How did I learn the correlation?
Same way I did learn many other things: patter recognition, direct experience, reading, confrontation with my peers.

So basically, you and your peers have established your own optical size comparison chart based on letters.
(As already explained, there is no correlation between bra cup sizes and the optical size of breasts. (Same applies to the volume and the actual size.))

This optical size comparison chart is kind of a simplified version of the two-number system above.
And if the breasts are confined in a bra, the second number of the made-up system is less relevant.

So using this optical size comparison chart might give you and your peers mostly identical results.

But outside that group, the information is completely worthless.
Every other group would have their own baseline and differences between the letters.

So if your group says D, the other one might say F

 

[SeriousBrainDamage]

By confrontation with my peers I just meant normal human interactions.
There isn't a restricted circle of people with whom I exchange thoughts about female bodies...
Wait a minute, maybe actually there is one, but it as nothing to do with what I meant.

Well, if you would want a system that roughly describes the optical size of breasts, I'd go for two basic numbers...
- BTCR (breast width to chest width ratio.) You would add the width of the broadest part of each breast, multiply it with 100 and divide that result by the chest width. If the number is 50, the breasts would be rather tiny. If the number is 100, they would cover the full front. If it is above 100, you would even be able to see the breasts on both sides if you look at the woman from behind.
- PF (protrusion factor.) This would describe how much the breasts protrude in comparison to the BTCR. It indirectly gives a clue about the horizontal roundness of the breasts. A number of 5 would mean that the breasts are hemispheres. A number below 5 would mean that they are flatter. A number 5 would mean that they are protruding so much that the radius center of the breasts is even in front of the chest base. 10 would mean that they are basically globes glued to the chest (extreme fake tits)

Your angle is that of a visual categorization, which is fine and maybe it's even better, easier to guesstimate, and also because it's safe to assume the average 'tester' looks to a bigger number of girls than what she/he actually gets to touch in their privates.
When I wrote down the upper, I did it with a more generic evaluation in mind, but you're right, as when you step into the touchy feely zone, it all gets more subjective, while proportions are as much mathematical as human bodies can get.

The question you all pose here seem to be twofold:

1- Cup sizes are not consistent with themselves. There's is no mathematical order and neither correlation between the measures of bras and the actual volumes of the breasts they are build to encase.(???)

2-Even putting aside point one (or specifically because of that), there's no unanimity on the value to assign to a given cup size. So if I say for istance that C cup is what I consider the average, not big and neither small, breast size of averge sized girls(average height and weight), everyone and their mother will disagree with me.

Well, I challenge both points.
I think claiming point one is silly, as the contrary is rather self evident.

Point two has a little more bite, but not so much when you consider the right premises.
When considering the averages, if you take national parameters of average height, weight and of course sizes, all population gets into the pot.
You loose track of the specific slice of pouplation you want to consider for this.
Do we care about super-overweight or elderly ladies? Nope, we don't, yet they fall into the mean of a specific country.
Now, I really don't want to say that but... well, lets go with this: some countries, richer countries, have overweight indexes of pouplation that flaw the measure.
If the average girl is overweight is safe to assume her breast would be a little smaller (nothing wrong with being a little overweight, it's just a matter of physical preferences) if she were closer to be fit.

When you think about a female character, do you picture her in your brain as chubby or overweight? Thicc maybe, is so popular with kids these days...
Don't answer right away.
You may do, but if you do, I bet you explicit it in her description, so it's safe to assume the majority of female characters have body proportions (breast aside) closer to ideal than the average population.
With this in mid, you may already see how countries averages count so little in realtion to this argument.
Ideal bodies are ideal everywhere, that's just what they are, ideal.

So, it's not very uself to the conversation if you come and reply

'C cup breasts are small in my country, not average'.

You wanna go with

'C cup breasts are small, not average for me because I'm a big guy'?

You know of that, right? You're a big guy, so the average feels smaller for you, yet you should get the description.
It's not like you would write a character stating she has average-sized breast meaning E-cup just becasue you're big, right?
You would rather describe her as much objectively as you can.
She'd be tall and voluptuos(not average) with big breasts(which to you must feel quite right).

What's left?

'C Cup breasts are small because of my own taste.' isn't that right?

But that's is just silly.ì if you think about it.
Do your tastes bend reality?
If I say :

'D cup breasts mean they are larger than the average'

you can't reply with

'for me G cup breast are larger than the average'.

I mean, yeah, that's techincally also correct, but it's also inaccurate.
In fact G cup breast are larger than most.

Are there bigger breast than that? Sure.
Are they common considering girls and womans with bodies close to an ideal of beauty?
Nay.
Are ideals of beauty all the same?
No.
What if my ideal of beauty deviates from canon?
Are you telling me you wouldn't precisely describe in what way and measure it deviates in your story?
Well, if you do, you will be still using the canonical ideal as comparison.

 

[Sune's Kiss]

I dunno, I still think using bra size to describe a woman's breasts is like using underwear size to describe a man's penis.

On that note though, if you want to utilise bra sizes in your story it's your story to do with as you please.

 

[gene.sis]

1- Cup sizes are not consistent with themselves. There's is no mathematical order and neither correlation between the measures of bras and the actual volumes of the breasts they are build to encase.(???)

I think claiming point one is silly, as the contrary is rather self evident.

There is a correlation between a value pair of a bra and a value pair of a woman's chest.
The whole bra sizing system is even "logical."

But it is only useful for its purpose of defining the size of bras.

To apply the system to
- optical size,
- actual size, or
- volume
doesn't work.

I think this should be clear with the models given in the previous posts.

So I'd say it's obvious that the cup size has no correlation to the optical size, the actual size, or the volume.

But I'm open to any mathematical model that proves this wrong.

safe to assume the majority of female characters have body proportions(breast aside) closer to ideal than the average population.

(side note: flawlessness is not exactly perfection)
The majority of characters will probably be of a slender build but there is still a wide variation to it.

The height might range from 5'2" to 5'8"
And they could be anything from fit to skinny.

So there is still room for very different band sizes that would result in different cup sizes for the same optical size.

With this in mid, you may already see how countries averages count so little in realtion to this argument.

Yes, countries' averages don't really mean a lot because they depend on so many things.

2-Even putting aside point one (or specifically because of that), there's no unanimity on the value to assign to a given cup size. So if I say for istance that C cup is what I consider the average, not big and neither small, breast size of averge sized girls(average height and weight), everyone and their mother will disagree with me.

Yes.
If you ask 10 girls, who have the exact (!) same figure including breasts, what bra size they wear, you will probably get 5 different answers.

So even if you have direct experience by being able to look at a woman's bra blurb doesn't mean you can tell her bra size.

That means that everyone can and will have a different perception of a certain cup size.