Finally, Bra Sizes Explained (2024)

Wednesday, July 24, 2024

Finally, Bra Sizes Explained (1)

How are Bra Sizes Determined?

On top of being highly technical garments, bras are also complicated in the way their sizing works. For example, a woman who wears a 32G cup isn’t necessarily a true G cup. Confusing, right? But stay with us — we’ll explain how bra sizes work in just a bit. It’s no wonder that 80 percent of women are wearing the wrong size when one’s cup letter doesn’t directly translate to their cup volume. See why your measured bra size may not be your actual bra size.

How to Find Your Bra Size

First things first, let’s talk about sizing a bra the traditional way. Bra size measurements are calculated based on your band size (number) and cup size (letter), which are typically determined by using a tape measure around your rib cage and bust. If you’d rather skip the dressing room, ThirdLove offers an online Fitting Room Quiz that matches you with your bra size and recommended style based on your unique breast shape. Regardless of what method you choose, you’re left with a number and letter that is your bra size.

How to Determine Bra Cup Size

Now, here’s where things can get a little tricky. For reference, any cup with a 34 band size is considered a “true cup” size. This means that a 34AA is in fact a AA cup, just as how a 34B is a true B cup. However, a 34B is also equivalent in cup volume to a 30D, 32C, and a 36A. All three aforementioned sizes are a B cup despite what their cup letter indicates. This is called sister sizes.

Take a look at our bra size chart below for reference. All bra sizes in the same row across share the same sister size, aka they’re all equal in cup volume. Let’s do another bra cup size comparison: if you wear a 32D, you are actually a true C cup. An easy way to determine your true cup size is simply to locate your bra size on the chart below and see which cup letter is paired with a 34 band in your row.

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The Importance of Sister Sizing

Knowing your sister size can be helpful when adjusting your bra size. For example, if the cups fit comfortably, but the current band size is too loose, you’ll have to try a smaller band size as well as a larger cup size to maintain the same cup volume. So if you were in a 36F, going down in the band size alone would result in a cup size too small. Though the 34F sounds like it has the same cup volume as the 36F, it’s actually one cup size smaller. To keep the cup volume the same, you’ll need to try a 34G, which ensures a snug and comfortable fit, while maintaining the same cup volume as the 36F.

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How Should a Bra Fit?

There are a few things to check when trying on a new bra to determine whether it fits you well:

  • Cups. While you’re wearing the bra, your breasts should each rest within their respective cups. The cups should cover the entire breast, with your nipples sitting at about the halfway point of the cups. Further, there should be no cup gaping or spillage.
  • Band. The band should fit you snugly without being too tight. It should sit flush against your skin, just loose enough that you could put two fingers beneath it. Remember that the band provides most of the bra’s support, so this is crucial.
  • Straps. The straps of the bra should stay up on your shoulders without slipping down. They shouldn’t be so tight, however, that they dig into your skin or cause other issues.

Find more information on how a bra should fit on our website.

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Common Bra Fit Issues

Many women struggle to find a good-fitting bra. Watch out for these common fit issues when bra shopping:

  • Cup gaping. One common bra fit issue is cup gaping. This is a fit issue where there is space between the breast and the cup of the bra. Usually, this issue indicates that the cup size is too large. Consider going down a cup size or going with a sister size.
  • Spillage. Some women find that their bra causes spillage. The most common types are front, back, and side spillage. This issue can create awkward silhouettes beneath clothing and feel uncomfortable to the wearer.
  • Band fit issues. If your bra band is too tight or too loose, it may be uncomfortable or make your bra less supportive. The band should fit snugly but not too tight when set on the loosest hook. Also, keep in mind that if you notice hair-like fibers coming from your bra band at any point, this indicates the elastic has broken. You’ll need to replace the bra as soon as possible to ensure you have a fully elastic and supportive band.
  • Underwire discomfort. If your bra is the wrong size, it may cause the bra’s underwire to dig into your skin. This could be painful and even lead to infections down the road, so it’s critical to ensure a bra’s underwire fits you correctly before buying it.
  • Straps too tight or too loose. If your bra straps are too tight, they may leave indentations on your skin and cause discomfort. If they’re too loose, you may find yourself needing to pull them back up every so often. Opt for bras with adjustable straps and non-slip features for the best results, and ensure you get your correct bra size.

Differences in Bra Sizes Depending on Bra Type

So, how do bra sizes work for different types of bras?

There are two primary ways of sizing bras depending on type. The first is standard bra sizing, which indicates the band size (a numeral) and the cup size (a letter). Some breast or bra size examples you might see according to this sizing method include 34A, 38B, and so on. This is the way that most bra types and styles are sized, making it essential to familiarize yourself with your own traditional bra size and its sister sizes. At ThirdLove, our bras come in a huge range of band and cup sizes, even including half cups so you can find your perfect fit!

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The other way to size bras is more simplified. Certain types of bras, such as sports bras and bralettes, come in sizes XXS through XXL instead of in specific band-cup size ranges. These bras tend to be less structured, making this simpler range of sizes realistic. At ThirdLove, we recognize that there are a lot of people looking for wireless bralettes, bras, and sports bras that still require good support to feel comfortable. That's why we created wireless bras withPrecise Sizing™, offering 3x more sizes than other wireless bras to account for larger and smaller cups. Our wireless bras will provide amazing support for up to G cups!

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Similarly, we know howawful sports bras can be. We found that most were either comfortable but unsupportive, or supportive but restricting and uncomfortable. That's why we designed a better sports bra! Our Kinetic Adjustable Sports Bra comes in your regular bra sizing to provide you with the best support and comfort possible, regardless of your size!

$78

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Need help with sizing? Take the Fit Quiz or Chat with a fit stylist

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Find Your Perfect Fit at ThirdLove

There is a lot to think about when looking for the perfect bra! At ThirdLove, we offer a variety of bras in a wide range of sizes, even including half cups, to suit every shape and size. If you’re still not following along (you’re not alone!), you can always take our quick onlineFitting Room Quizto figure out your perfect fit.

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Finally, Bra Sizes Explained (2024)

FAQs

What is DDD bra size equivalent to? ›

Is a DDD the same as an F? It might seem confusing, but yes a DDD is the same as an F— sometimes they are labeled differently based on the brand. After size D you can either go up to size DD which is the bra size equivalent to size E, size DDD which is equivalent to size F, and size DDDD which is equivalent to size G.

What does a 34 B look like? ›

This is what 34B looks like. 34B *roughly* indicates a 34" underbust and 36" bust (B = 2 inch difference between underbust and bust measurements), however, bear in mind that 6 measurements are needed to calculate bra size as accurately as possible!

What is bigger, 32a or 34a? ›

A 34a is for an underbust of 34 inches and an overbust of 35 inches. A 32a is for an underbust of 32 inches and an overbust of 33 inches. These are very different measurements.

Is 34C the same as 36B? ›

The general rule is if you go up a band size, you should lower the cup size i.e., a 34C is bra size equivalent to 36B. Here's a breakdown for you. Size down: Go one size lower than your actual band size & go a letter higher than your cup size. So, if you're a 36B, your sister size will be 34C.

How heavy are DDD breasts? ›

The average pair of DDD breasts weighs between 15 and 23 pounds. To put this into perspective, this is the equivalent of carrying around two small turkeys on your chest every day. . . . . .

How do I know if I'm a DD or DDD? ›

DD will have 5 inches of difference from your band size, and DDD will have 6 inches of difference. DDD is also often recognized as an F cup.

What bra size is considered big? ›

What Cup Sizes are Considered Plus Size. As mentioned above, a Cup Size DD and larger and a Band Size of 40 or greater is categorized as a plus-size bra. Therefore, if your cup size is DD, DDD, E, F, G, H, I, or K, with the required Band Size, you need to shop for plus-size bras.

Which breast size is good? ›

In a functional and aesthetic sense, the ideal breast size for a woman is generally considered to be one that's proportionate to their height, shoulder, and waist diameter. So, for women who measure 5'3, their breasts should complement the frame of their body and allow them to move freely without discomfort.

Is 34 a good breast size? ›

The average bra size in the United States is 34DD. That said, average breast size does not necessarily equate “normal” size. Average breast size can vary by country. In the U.K., for example, the average is 36DD.

What if the cup size is too big but the band fits? ›

If your bra cup is too big, but the band fits well, your best solution is to try a bra with the same band size but down a half or one cup size. For instance, if you wear a 36D and the cup is too big, but the band fits, try a 36C bra size. You do not need to try your sister's sizes for such a case.

How to go up a cup size overnight? ›

The notion of being able to make your breasts grow bigger overnight is a myth that needs to be debunked. While exercises help tone the muscles around the chest area, they do not impact tissue growth. We must embrace our bodies as they are, focusing on overall health, self-acceptance, and self-care.

Will a 30B fit a 32A? ›

A bra sister size maintains cup capacity while adjusting the tightness of the band, leading to a better fit in some instances. For example, if a bra is a 30B, its direct sister size up is 32A, while down is 28C.

Can you wear your sister size? ›

Yes, Sister sizes are sizes that have the same cup capacity but a different band size. For example, someone who wears a 32C could also wear a 30D and a 34B depending on if they want a tighter or looser fitting bra. Make sure you have been fitted and know your true cup size before trying to work out sister sizes.

How to go up a cup size in a bra? ›

Once your breast is pulled forward, if the tissue is not completely in front of the wire, you need to go up in your cup size. For every 3/4 inch of breast tissue under and behind the wire, go up one cup size. If you have never been fitted, it is likely that you will need to go up several cup sizes.

Why do bras have sister sizes? ›

The idea is if you go down an underband size and go up a cup size, you should have a similar fit. And the same if you were to go up an underband size and down a cup size. Finding a sister size can be convenient if your measured size is unavailable!

Is DDD the same as F or G? ›

What about DDD sizes? DDD is most commonly used in the US, and converts to an E or F cup in UK sizes – one size up from DD. Many larger cup bra brands use UK sizing, so it's worth being familiar with how sizes convert. Our international size charts cover the differences at a glance.

Is DDD the same as G in cup size? ›

What about DDD and G cup sizes? In American bra size, A DDD cup is also called an F cup, which sits just one size above a G cup. It means that they differ by just one inch. A seven-inch difference between bust and band is a DDD or F cup.

What is my bust size if I wear a 34 DDD? ›

Bra Sizes
DDD SizesUnder BustFullest Point
32DDD26"-31"36"-38"
34DDD28"-33"38"-40"
36DDD30"-35"40"-42"
38DDD32"-37"42"-44"
4 more rows

How big is 32DDD? ›

32 DDD nominally equates to a tape measure of 38″ when measuring around the fullest part of the bust. The DDD designation of cup size is not uniform across manufacturers, or even sometimes across different style bras by the same producer.

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