This Is How Bra Size Works: The Meaning Behind the Numbers

It’s hard to understand your bra size without a little research homework, and it’s frustrating when you want to find the right size but all the numbers seem confusing to you. Or maybe, you’ve been wearing the wrong size of bra? (Read 5 Signs You’re Wearing the Wrong Bra). But, worry no more, in this article, we are going to break down how bra size works so you can better understand bra sizing numbers. 

how bra size works


Image via Wikipedia

What are the numbers and letters can tell you

When we talk about bra sizes, we are talking about bras that have a letter and number sizing system. Typically, they start with a two-digit number, followed by a letter. These following are some examples:






The number represents the band size of the bra. It refers to the size of your ribcage/torso, which is located directly beneath your breasts. However, this varies depending on the region and also the brand itself.

As for the letter, it refers to the bra’s cup size, which is basically the size of your breasts. The cups become larger as you progress through the alphabets, so the farther the alphabet, the bigger the cup sizes. The way cup letters are arranged differs depending on the brand too. For example, some bra companies will use DDD cups, meanwhile others may use E cups to represent the same size of cup.

The bra cup size and band size are linked and dependent on each other, meaning that there is no “A” cup or only “36” band size, as they will not be able to accurately determine your breast size. “I’m an E cup” is too general of an answer to indicate what bra size you are.

Band sizing criteria

how bra sizing works


Image via Queensfair

Band size is the circumference of your ribcage which is located right under your breasts. Most women find that the greatest fit for band size is the nearest measurement to their underbust. This is mostly based on your personal preferences as some prefer a tighter band while some prefer it a little looser. 

Despite, it is highly recommended to find a bra with band size that fit yours just right. Wearing a bra that is too loose can give your breasts lack of support. Besides, a band size that is too tight will not only cause discomfort but also health issues such as skin irritation and even more, acid reflux. This is so because according to Heather Downes, MD, on Healthline, when you wear a bra that is too tight, the pressure on your intra-abdominal increase which can lead to the situation where acid in your stomach gets pushed to your lower esophagus. Therefore, if you feel that your bra is digging into your skin, you might need to change it with the one that has larger band size.

Cup sizing criteria

bra sister sizing


Image via Eva’s Intimate

For most of the bra brands, the difference between one cup size is an inch. The cup size always relies on the band length, so a 34D and 38D is a totally different size because the band length is different. A woman who wears a size 34D bra has a smaller breast circumference than a woman who wears a size 38D bra. 

Because cup size is proportional to band size, this simply means that their breast circumference and band length has the same amount of difference. However, always remember that not all bra brands will use the same measurement of “one inch increment equals to one size larger”. As an example, Avocado uses a difference of 4cm between cups. So, it is always better to follow the measurements of the bra instead of the sizing labels because they may be different from the previous brands you’re wearing.

What does the double letter mean?

According to Bratabase, double letters are just one more cup increment. For example, the increment difference between a DD cup and an E cup is the same as the difference between a B and C cup. Since every bra company decides on their own labels and sizes, always try the bra on or refer to their measurements to make sure they fit you well.

While bra size labelled on the bra is an important indicator to help you determine whether they are the right size of bra, it is best to follow the measurement of the bra, as there are different bra conventions depending on the region. So, always make sure the measurement of the bras fit you even though it is labelled with your bra size.

What bra sizes are there?

As mentioned, bra sizing is different depending on the brand and the region. You might also be wondering, what is the largest size of bra? In fact, the bra cup size can be as large as T cup and the band size won’t stop at 42. Some women might have to wear a bra with 64 band size. However, there are not many brands provide a bra with a wide range of size. Hence, some of us are not aware that the bra size is not limited to 42G and it’s also difficult for women with large busts to find the bra size that fits theirs.

We totally understand the struggle of women to buy the right bra size for themselves. Although it may be tricky to find the right size of bra, you can actually do your bra sister sizing by yourself at home by understanding on how to measure your bra size. If you have any questions that make you think you’re unclear about how bra sizes work, don’t be shy! We welcome you to DM us on our Facebook page to drop your questions so we can help you!


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