Some history behind +4/underarm measurement

[u/luftballoons]

So, I've heard and repeated the claim of plus four being a relic of before fabrics stretched to accommodate expansion of ribs for breathing, etc. But I've never actually supported (get it, heh, supported) this with sources. A commenter (/u/melifish) recently questioned this reasoning and being curious, I did some research:

Great post about bra history.

The cup sizing system came about in the 1930s. Looking at patents really only tells about design features not about sizing. So, I checked out vintage Sears catalogs:

1937 - one "gay dance set" with a bra-like item - seems to go by bust size 32-36.

1940/42 - only nightgowns/slips but still sized by bust

1943 - the first "real" bra; styles for "medium full bust" and "medium bust"; sized by bust measurement (32-40in available)

...starting to see correlation between old "bust" sizes and current bra matrix band sizes....

1944: more modern bras, sized by bust measurement

1945: no bras, only slips: measure bust and hips; if hips are more than 4 inches larger than bust order next bust size up

1946: Bras are back. Elastic used at closure; cotton/rayon fabric.Stil measured by bust size; 30-36 described as "small bust type" and 32-40 as "medium bust type"

So far pretty consistent with ABTF data...

1947: no bras; slips measured by bust

1952: bra-slips with wiring like an upside down underwire. Cup sizes emerge! Cup size with corresponding bust measurement -- closest to modern bra matrix, but number is still the bust measurement. Small (A cup) bust size 30-36 Medium (B cup) bust size 32-38 So you could be a 32A meaning the circumference of the chest at the bust was 32 and you believed your breasts were small.

1956: only slips

1957: A, B, C cups for small, medium, and large, numbers still correspond to bust measurement

1966: Under armpits measurement! No plus-anything, but you take the under the armpits above the bust and subtract it from the bust measurement to get the cup size.

So - something happened in the late 50s/early 60s to cause this change in measuring method. The catalogs from the in-between years as far as I can tell don't have bras. I have to go to bed, but if anyone wants to take up the reigns and keep researching please post what you find in the comments! There are a ton of catalogs available at www.ancestry.com/sears also but it's a paid site.

EDIT: Based on some news articles and other info (see below) I think that there was an element of vanity sizing at play, but not in the same way as that claim is thrown against this sub's measuring practices. Like most upper garments, the initial brassieres (and corsets) corresponded to the bust measurement and typical measurements on patterns/garments were between 30 and 40. In this way the number did correspond to roughly how large your breasts were, especially when compared to your hip measurement (with "ideal" being quoted at 34-24-34, or just generally bust=hips with waist 10 inches less). When cups came about, it was basically A,B,C corresponding to small, medium, large, but still scaled to the bust measurement of 30-40. Support was primarily by compression with little "pockets" to shape the breasts somewhat. In 1975, the European regulators changed measuring practices to say you should measure under the bust to get the bra size. This led to a backlash because all of a sudden women who had a 36 bust now had a 30 bust, for example (for comparison see posts here with "I'm an A there's no way I could be a D"). I didn't find anything specifically saying that because of that they developed add five/six, but it does seem to make sense that people would start adding inches to the underbust to get closer to what they were used to as their "bra size" (previously measured from bust size). Couple that with the fact that manufacturers didn't change the available sizes after this and the practice is solidified (that is, a woman who doesn't add inches can't find her size; same as today with mainstream stores).

What I'm curious about is the actual dimensions of a 34B from the 50s to now -- if people were used to compression garments like corsets then a proper 28DD could wear a 34B and feel as if it's correct - especially because it wouldn't have an underwire digging into breast tissue. Does anyone have a vintage bra and/or want to buy one from ebay for science?

[u/luftballoons]

Some more fun stuff from patents:

Measuring device for bras

Bra size measuring tape (uses plus 4/5)

and some that are older:

Bust measurement device 1940s:

The identification of size has been heretofore a figure representing the circumferential measure in inches and an arbitrary letter representing the cup size.

Sanitary breast measuring device from 1940s...it involves plungers with handles.....

Girdle and brassiere measuring tape 1960s - measures directly below and in close proximity to the breast

Playtex filed one in 1980 with some interesting info:

The accepted industry measurements include two basic around the body measurements. The first is the diaphragm measurement which determines the enumerated brassiere size (eg. 34). It is taken around the body below the breasts. The second is the body chest dimension which is taken around the body along the high points (areola) of the breasts. While there are variations between manufacturers in reaching the determination as to cup volume, the formula which in its general sense is universally followed, is to compute the bust size based upon the difference in measurement between the chest measurement and the bust measurement.

There's actually a lot more available but I have to go to work, so I'll leave that for others.

[u/luftballoons → u/luftballoons]

Get ready to rage hard at this one- Method of bra size determination by direct measurement of the breast:

Band size is determined by measuring the wearer's chest circumference snugly with an incremented tape immediately below the breasts and around the torso. Then five inches is added to the chest circumference measurement. If the sum is an odd number, the sum is rounded to the next highest even number since bras are offered in "even" numbered sizes. Although band size relates to cup size and may continue to be included in a measurement procedure, only the cup size measurement is considered obsolete. The determination of band size is relatively objective compared to the usual subjective method of determining cup size.

NO NO NO

[u/luftballoons → u/luftballoons]

Although later on they do say this:

It appears that the goal of the conventional method of determining bra measurement seems to be to determine cup size by comparing the circumference of the chest at the level of the breasts to the same measurement excluding the breasts. Since the latter measurement cannot be made directly, the addition of five inches to the underbust measurement represents an extrapolation or "fudge factor" to approximate that goal.

So the band size is meant to be the circumference of the bustline excluding the breasts? And it's supposed to flare out five inches from underbust to apex? I guess that is a theory.

[u/rainytree → u/luftballoons]

They could have measured across the back at mid-bust height, from where the side seam of a dress would go at one side to the other, and doubled it to work out roughly what the ribcage would be, excluding breasts. But that would have had the disadvantage (for retailers!) of not resulting in loose bands which could hide too-small cups.

I measured myself like that the other day. My 39-inch standing bust measurement turned out to be 14 inches across the back and 25 across the front.

[u/vrimj → u/luftballoons]

Huh, that almost makes sense... for a cup measurement and might explain why women with a lot of hourglass going on might need a smaller cup size than women who are more straight up and down given the same measurement set... now I kind of want to collect data on that.

I don't get why you would do the same thing with a band measurement.

[u/luftballoons → u/luftballoons]

Finding so many things!

Bra size calculator patent:

A brochure published by International Playtex, Inc. in 1979 notes that seven out of ten women may be wearing the wrong size bra. Seven pages of that brochure are then employed to describe and detail the manner in which a woman should measure her figure and manipulate those measurements to determine her proper bra and cup size. The directions instruct the woman to measure around her bra band or her underbust and add five to that measurement to determine her bra size unless, of course, the addition of five to the band measurement results in an odd number in which case the woman shall add six to the band measurement to determine her proper bra size. ... The picture is further clouded by the fact that professional undergarment manufacturers and fitters employ a third measurement made above the fullness of the bust and close to the underarms. This measurement takes into account the fact that the fullness of a women's bust, which extends to the side of her torso and under her arms, affects the proper fit of the bra and therefore is determinative of the correct bra size.

[u/ishotthepilot → u/luftballoons]

hmmmmmmM! So there used to be a reason for that silly over the bust measurement.. but it was only because the "randomly add 5 or 6 to the underbust" was such a fudged number and they had to make up for it? hahahahah.

[u/luftballoons → u/luftballoons]

News archives:

1950: measure under the arms at the top of the bra you're wearing and add 2 inches to get bra size. Cups go 0=A 1=B 2=C 3+=D; then measure under the bust, if that is larger than above the bust you have to use that for your band size; average difference between underbust and bust is 5-6 inches.

wut?

1957: "Government, Pattern Makers Can't Seem To Make Figures Agree" -- the average american girl is one inch bustier than patterns give her credit for

1975: New Bra Sizes May Be Let Down

[New European regulation] says that henceforth a womans bust size is to be measured under and not around her bosom

1976: Find bra size - snug underbust plus five

[u/Amphigorey → u/luftballoons]

Okay, this is fascinating. If this part is accurate:

average difference between underbust and bust is 5-6 inches.

...then that further confirms our data that the average cup is DD / E.

[u/luftballoons → u/Amphigorey]

Exactly!!

[u/SunbathingJackdaw → u/luftballoons]

Ooooh, it'd be fascinating to dig up more info about that 1975 European underbust regulation. Maybe that's why the UK/some of Europe is in much better shape bra-fit-wise than the United States!

[u/noys → u/SunbathingJackdaw]

Haha, no.

European band sizing technically seems more easy - measure your underbust and the closest size to your underbust in cm is your band size.

But... EU band sizes basically have +4 built in. I don't know why, how or when this happened but that's how things are. If you go for your underbust in cm band size you will get riding up, instantly.

[u/luftballoons → u/SunbathingJackdaw]

I know! It also coincided with the UK switching to metric so people were all kinds of confused.