breast size around the world
Average Breast Size & Bra Size in the USA & World

Average Breast Size & Bra Size in the USA & World

Dana Donofree
5 min read

What’s the Average Breast Size and Bra Size?

Did you know that the average breast size and bra size changes depending on where you live? What about your breast size -- did you know that it can continue to change as you age? Believe it or not, there are several factors beyond body composition that determine your breast size. Read on to learn more about some of these influences and how they can impact your body throughout your whole life.

What’s The Average Breast Size In The U.S.? 

While it’s really difficult to precisely determine the standard breast size in the U.S. (or anywhere in the world, for that matter), we do know that the average breast size in America is a 34DD. A lot of factors, including wearing the wrong bra size and breast augmentation, may unduly influence this final figure, though.

What’s The Average Breast Size In Different Parts Of The World?

It’s only natural that breast sizes vary around the world! This small sampling from six other countries shows that breast size can vary wildly depending on where you’re from, ranging from an A cup to a DD cup.


Average Breast Size 









New Zealand 




South Africa 


How Do Countries Measure Breast Size And Bra Size?

The general rule of thumb when measuring breast size around the globe is by cup and band size, although the way breasts are measured in each country can differ. To measure your cup size, you compare the measurement of the fullest part of your breast to your underbust. The greater the difference is between the two, the larger the cup size you have. When you measure your band size, it is easiest to take a measuring tape and wrap it underneath your bust. If you land on an even number, that is your band measurement. If you land on an odd number, it is best to round up, because American band sizes are measured in two-inch even-numbered increments.

However, while the process to measure for a bra is generally the same, bra band sizes and cup sizes tend to be different depending on where in the world you’re buying your bra. This is not uncommon among all kinds of clothing; you can expect to see different measurements for jeans, shoes, and tops, as well as bras.

For starters, the units of measure are different. Bras sold internationally, listed as “INT” or “EU,” are measured in centimeters, while measurements marked “US” are in inches. That means a 32 band size in the U.S. is a European or international 70. European sizes increase by 2 centimeters just like U.S. sizes increase by 2 inches, but the difference between 2 centimeters and 2 inches is significant, which can complicate matters a bit.

In addition, while you may measure to be a B cup in the United States, it doesn't mean you will necessarily be the same size in another country. Some countries go by different size cups than the U.S. For example, what may be an A cup for Americans is a B cup in countries such as France, Japan, and Spain. 

measuring breast size

What Affects Breast Size?

Surprisingly, many things can affect the size of your breasts. A few factors include: 

  • Genetics: If your mom, aunt, or grandmother had small or large breasts, that can impact your breast size as well. 
  • Workout routine: The muscles behind your breasts can impact their appearance. While it may not actually make your boobs any bigger, it can help with lift; therefore, they may look larger.
  • Climate: Believe it or not, hotter or colder weather can influence breast size. Researchers believe this is because our bodies burn more energy, stored as fat, to keep cool in warmer climates.

Can Breast Size Change Over Time?

It’s 100% possible that your breast size can change over time! A few examples include: 

  • Pregnancy and breastfeeding. Not only are you carrying a tiny human, but your breasts grow several cup sizes in rapid time while your body prepares to nurse the baby. That’s because your body produces more progesterone, a hormone that prepares your body to carry a baby and to produce breastmilk. As you produce milk, your breast size will continually change and may even remain a different size once you’re done breastfeeding.
  • Menopause. The stages of life can greatly impact the size of your breasts far beyond puberty when your breasts first develop. When you reach menopause, your breasts may change size because your body produces much less estrogen, a hormone that stimulates milk duct growth.
  • Weight gain or loss. Your breasts are made up of two tissue types: supportive tissue and fat tissue. The latter tissue type is influenced by weight gain or loss just like any other part of your body that has fat.
  • Periods. Your menstrual cycle can affect the size, texture, and shape of your breasts. As your period comes closer, your body tends to produce more progesterone, which causes swelling and a change in breast size. You may also experience a change in breast size if you take birth control. 

How Does Breast Cancer Affect Breast Size?

Breast cancer may change the size of your breasts depending on the type of treatment your doctor decides is best for your diagnosis. A lumpectomy, which removes the cancerous breast tissue as well as some normal tissue, can change your breast size. Unilateral mastectomy and a double mastectomy, which is the removal of one or both breasts, will also influence your bra size. You may also have asymmetrical breasts as a result of breast cancer treatment or surgery.

How Does Breast Reconstruction Affect Breast Size?

Depending on the breast cancer surgery you undergo, breast reconstruction will determine your new breast size after treatment. 

Generally, there are two types of reconstruction surgeries patients undergo: flap and breast implants. 

  • Flap reconstruction involves relocating your body’s tissue with a connected blood supply to form a breast shape. This depends on how much fatty tissue can be relocated during the reconstruction process. Your final result may be anywhere from an A cup to a DD cup, but this depends on your surgeon’s recommendations. 
  • Implants involve placing inserts above or underneath your chest wall to recreate or augment your current breast size. Typically, your surgeon will not make your breast size much larger than what you’re used to; you can expect to have a B, C, or D cup after this procedure.


Unfortunately, there’s no right answer as to how breast reconstruction can affect your breast size. It’s best to discuss your options with your surgeon and advocate your desires and see if it’s achievable. After all, you will be the one living with the results, so it’s important that the result is something you’re happy to have every day.

anaono bras for breast cancer

Shop AnaOno To Support Your Breasts At Every Size

At AnaOno, we know that breasts are not all built the same. Whether your breast size changed after pregnancy, you need a little more support after menopause, or breast cancer surgery has altered your breast size, you’ll find the right bra for you at AnaOno. Everyone’s body has unique needs for support and comfort, and we are here to make bras work for you, not the other way around. Get started by exploring our bras, organized by which styles will work best for your body.

See Our Fit Guide for Post-Op Chests


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Dana Donofree
Dana Donofree

Founder and CEO of AnaOno. After a diagnosis of breast cancer in her late 20’s, Dana took her own lived experience and fashion design background and (re)designed intimates for those that have undergone breast surgery. Dana’s story has been published around the world in outlets like New York Times, BBC, Huffington Post, The Today Show, and more.