What is my bra size? (2024)

The Bra Secret You Should Know About

If you've found that finding your right bra size is a frustrating process, there are some sizing hacks that can make finding your perfect fit much easier. One of the most effective of these is the use of “Bra Sister Sizes”. You may be unaware that every bra size has several "Sister Sizes"- these are sizes which have an equivalent cup capacity, despite the letter of the cup size being different. Knowing your sister sizes can help you find your best fit when buying bras that run smaller or larger than normal.

It’s a common misconception that the larger the cup size, the larger the bra, no matter what the band size (i.e. a 32F is larger than a 36B, a 34C is larger than a 38A, etc). However, this is not the case. During the bra manufacturing process the same exact bra cup may be paired with different band lengths to create multiple bra sizes. For example, the same exact cup is used to make 38A, 36B, 34C, 32D, AND 32DD bras! The reason for this is that within each cup size (A, B, C, D, DD, etc), as the band size increases, the cup size also slightly increases even though the letter does not. For example, a 34B bra and 36B bra will not only have different lengths, but the capacity of the cups will also differ. Once you understand that there are equivalent “sister sizes” to your own bra size, it can help you solve any bra fitting issues you may have.

Bra Sister Size Size Comparison Chart:


Each row shares the same cup size and each column shares the same band size.
Sizes in black are sizes we make. Sizes in light gray are sizes we dont make.

30 BAND SIZES

Sister Size DOWN

Current Bra Size

Sister size UP

28B

30A

32AA

28C

30B

32A

28D

30C

32B

28DD

30D

32C


32 BAND SIZES

Sister Size DOWN

Current Bra Size

Sister size UP

30B

32A

34AA

30C

32B

34A

30D

32C

34B

30DD

32D

34C

30DDD

32DD

34D

30F

32DDD

34DD


34 BAND SIZES

Sister Size DOWN

Current Bra Size

Sister size UP

32B

34A

36AA

32C

34B

36A

32D

34C

36B

32DD

34D

36C

32DDD

34DD

36D

32F

34DDD

36DD


36 BAND SIZES

Sister Size DOWN

Current Bra Size

Sister size UP

34B

36A

38AA

34C

36B

38A

34D

36C

38B

34DD

36D

38C

34DDD

36DD

38D

34F

36DDD

38DD


38 BAND SIZES

Sister Size DOWN

Current Bra Size

Sister size UP

36B

38A

40AA

36C

38B

40A

36D

38C

40B

36DD

38D

40C


Common Fit Problems and How to Solve them Using Sister Sizes:


If your cup fits but you need a different band size.

What is my bra size? (1)

To change your Band Size and keep the same Cup capacity, remember that the 36C with cups that fit you (for example) has the same cup capacity as the 34D with the smaller band size and the same Cup capacity as a 38B that has a larger band size .Getting your best fit will require both the band size AND cup size to change. For another example, if you are wearing a 34B bra and the band is tight but the cups fits well, instead of going up to a 36B, you should choose your equivalent sister size, 36A.

If your band fits but you need a different cup size.


What is my bra size? (2)

If your band fits great but your cups are too big or too small, keep the band size the same and just adjust the cup size based on your needs. For example, if you are wearing a 34B bra that fits in the band but has cups that are too small, you should choose a 34C.

If both your band and cup don't fit.

What is my bra size? (3)

If you both the band and the cup are a bit loose, the band should go down and the cup capacity should go down too. Remember that with a smaller band bra, the same Letter cup size is going to be smaller. For example, if you are wearing a 34B that is too loose in both the band and the cup, try a 32B. It's a smaller bra, so the same Bcup in a 32 is smaller than a Bcup in a 34. If you have a 34B that is too Tight in both band and cup, get a bigger band, and remember that in a bigger bra the same Cup Letter is bigger too. So a 36B is bigger in band and cup. By knowing your correct bra size, as well as what your sister sizes are, you will be able to choose the best option to give you a perfect fit. ! For more sizing help, international size conversions, or to try our new mobile sizing app, please go to our Sizing Help page by clicking here.

What is my bra size? (2024)

FAQs

How do you calculate your bra cup size? ›

All you need to do is a little bra math: Subtract your band size from your bust measurement to find your cup size. “The difference in inches corresponds to your cup size,” says Iserlis. For example, if your bust measures 37 inches, and your band size is 34, the difference will be 3.

How do I know my bra size B or C? ›

If there's a 1-inch difference between bust and band you're an A cup; 2-inch difference is a B cup, 3 inches is a C cup, 4 inches is a D cup, and so on. For example, if your bust measurement is 37 inches and your band is 33 inches, you would be a D cup because of the 4-inch difference.

How do I measure my bra size myself? ›

Stand upright without a bra on, and using a measuring tape, measure around your back and under your bust, where the band of a bra would usually sit. Make sure the tape is going around in a steady, even line. It should feel snug, but not tight. Measure in inches: if you land at an even number, that is your band size.

Is 34C big or small? ›

A 34C breast size indicates that the underbust measurement is approximately 34 inches, and the difference between the underbust and bust measurements is around 3 inches. It suggests a moderate breast volume relative to the band size, creating a proportional and balanced appearance.

Is DDD the same as F? ›

Here in the US, DDD is the same as F. But, if you were bra shopping in the UK, for example, DDD/F would be E. Some US-based brands don't always get this distinction right, and bra size charts aren't always consistent.

How to know your bra size without measuring? ›

You don't need to use a tape measure to find your bra size! Take one of your current best fitting bras – even if it's not very well fitting at all, and fasten the bra on whichever hook feels most comfortable. Adjust your straps to a two-finger tension, and scoop and swoop all your breast tissue into the cups.

How to measure bra size without bra? ›

Stand upright without a bra on, and using measuring tape, measure around your back and under your bust, where the band of a bra would usually sit. Make sure the tape is going around in a steady, even line. It should feel snug, but not tight.

Is 34B or C bigger? ›

In standard bra sizes, the number denotes band size and the letter denotes cup size. So 34C has a bigger cup size than 34B but the same band size.

What is the smallest bra size? ›

What is the Smallest Bra Size? The smallest bra size is generally 28AA, but some places (particularly specialist retailers) will produce AAA cups. 28AA means that the bra band is 28 inches and the bust is less than one inch larger than the ribcage.

What is the biggest bra size? ›

However, cup sizes can vary widely between brands, so it is important to know your bra size before shopping for a new one. The largest cup size in the world is an H cup, which is available from some European brands. Band sizes typically range from 28 to 44, but some brands offer larger or smaller sizes.

What is the cup size of 36? ›

The cup sizes that are commonly available in a 36 bra size are B, C, D, DD, and DDD. However, this can vary depending on the brand and style of the bra. Some brands may offer larger cup sizes, while others may offer smaller sizes.

Is 34C a big bust? ›

Most of the women who have a moderate structure come under 34 and 36 band size and B or C cup sizes. When it comes to 34c bra size, it gets fit to the woman with a medium bust size, neither small nor big. It is one of the outstandingly elegant bra sizes.

Should I go up a cup size or band size? ›

If you go down in the band size, you need to go up in the cup size to maintain the same cup volume. On the other hand, if you go up one band size, you should go down one cup size. For example, if you wear a 36D, your sister sizes are 34E on the size down and 38C on the up.

How to tell if your bra cup is too big? ›

This one is fairly simple to recognize. When you look down at your bra do you notice space between your breasts and the cup? If so, it's too big. If you aren't able to see any gaps while standing up, try leaning over while looking into a mirror.

Are bra calculators accurate? ›

And many calculators forget about crucial factors like breast shape and how cup sizes are determined, which both have a major impact on whether or not a bra will fit. Traditional calculators also don't take into account the fact that bodies change over time due to things like weight gain or hormones.

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