Bra Cups 101: Why and How Bras are Measured in Cups

The most common answer from our Fit Quiz was 34B. Many of us know that the “34” represents the circumference of your torso in inches, but what does the B cup size indicate?

Bra cups have been measured in ABCD sizes since the 1930s, but the definition of what the cup size measured has changed slightly.

When bra cups were first introduced, they were sized according to how the breast fell in relation to the body. Now, bra cup sizes are based on how far your breast projects away from your torso.

The First Bra

Over 100 years ago, in 1914, Mary Phelps Jacobs (later known as Caresse Crosby) received a patent for the modern idea of a bra (which you may have read in our Every-woman’s Encyclopedia of Bra Styles!).

She eventually sold this patent for $1,500 USD, or today’s equivalent of $21,000, to Warner Brothers Corset Co.

Image of the first patent for a brassiere, which features a hand-drawn sketch of the first bra.
3rd November 1914: A copy of the first patent for the brassiere, filed on 12th February 1914, by Mary P Jacob. (Photo by Hulton Archive/Getty Images)

The Warner Brother’s Corset Co. sat on the patent for a few years before introducing their range of bras that would revolutionize how bra cups were sized.

But before we get to that, you need to know about S.H. Camp.

The Beginning: S.H. Camp and Company

The practice of sizing bra cups with ABCD was started by S.H. Camp, an American corset company. In the 1930s, as bras were beginning to replace corsets as a woman’s undergarment of choice, S.H. camp (very subtly) marketed their bras as “anatomical supports”.

“Advertisement: Camp (S. H. Camp & Company).” Women’s Wear Daily Mar 22 1956: 29. ProQuest. 7 June 2019 .

The “anatomical supports” were sold in cup sizes A-D. However, the cup sizes were not based on the volume of different breasts, as they are today, but rather on how much they hung off of a woman’s body. You can see the difference in the sketches on the right-hand side of this 1932 advertisement.

While this sizing technique was popular for S.H. Camp-branded bras, it was not widely adopted by outside brands.

The Reinvention: The Warner Brother’s Corset Co.

Now let’s jump back to the Warner Brother’s Corset Co.

In 1937, The Warner Brothers Corset Co. (later known as Warnaco, to avoid confusion with the film company) introduced their ABC Alphabet Bras, which were offered in four types: Type A, for “small youthful busts”; Type B, for “average busts”; Type C, for “heavy busts”; and Type D, for “very heavy busts.”

A 1938 advertisement for the Warner Brother's Co. ABCD sizing of bra cups, which shows a woman wearing a bra, looking off into the distance. Bra cups illustration image
“Advertisement: A’Lure Alphabet Bra (the Warner Bros. Co.).” Harper’s Bazaar 08 1938: 144. ProQuest. 7 June 2019 .

These definitions indicate that the ABCD cup sizes corresponded to a woman’s breast volume, rather than another feature.

The bras became very popular, bringing in $1 million to the company by 1947.

A 1949 advertisement in Harper's Bazaar, depicting a sketch of a woman standing in her bra and underwear, and another sketch of her fully dressed.
“Advertisement: Warner’s Le Gant Alphabet Bras (Warner’s Le Gant).” Harper’s Bazaar 09 1949: 97. ProQuest. 7 June 2019 .

After the introduction and success of the ABC Alphabet Bras, many American and international brands followed suit and began offering their bras in the same sizing system.

Today, Warnaco owns Speedo, Ann Cole, and White Stag, among other brands, and has licensing agreements with companies including Christian Dior, Fruit of the Loom, Victoria’s Secret, and Ralph Lauren.

The ABC Bras are no longer for sale, but the A-D cup sizing is carried on through Warnaco’s partnered brands, as well as nearly every other international lingerie retailer.

Bra Cups Today

Today, brands around the world sell bras in cup sizes that typically range from AA to DD (E) or DDD (F).

Cup sizes measure the volume of your breasts, approximated based on the difference in circumference between your torso and your bust.

Your U.K. cup size can be calculated by subtracting the circumference of your torso, measured under your busts, from the circumference of your torso, measured on top of your breasts. A 1-inch difference indicates that you are an A cup, a 2-inch difference indicates B cup, and so on.

This scale differs across countries, however. While each UK cup size increase corresponds to a 1-inch increase in circumference, European and Asian brands increase by only 2cm. Therefore, the larger the cup size, the larger the actual size variation you will see between countries.

A chart that indicates the sizes of bra cups, depending on her bust and band measurements.
Chart taken from BlitzResults.

Remember that even between brands, there are many size discrepancies between lingerie brands, so your bra size will change depending on where you shop. You can refer to this chart below to get a loose idea of what your cup size may be, depending on where you live.

And, as a final reminder–size is just one aspect of bra fit. Shape, density, and preferences are just as important if we’re talking about finding the best bras for your body. If you want to know more about your breast shapes and which type of bra cup is best for you, head over to our Fit Quiz!

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