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How Big Will My Boobs Be?

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Many ladies are wondering how big will their boobs be, especially if they are just starting to grow. You should know that breasts will develop at different ages and at different rates. Even your two breasts can have different proportions, too. So, let’s talk about how big your breasts can get through this article.

How Big Will My Boobs Be?

In the United States, the average size of a bra is 34DD, which means that your breasts can grow up to 30 ½ inches for the bust and 38 inches for the cup size. In the U.K, however, it is 36DD. The size of your breasts differs because of your age, genes, and your weight.

These sizes will also differ from one lady to another. Their breasts can get bigger than 34C cup or smaller than a 32B cup size. The size of your breasts can also change during your monthly period, during pregnancy, after giving birth, and while pumping and nursing. Woman wearing a green jacket over a pink bralette

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What Determines the Size of My Breasts?

Here are the reasons why some women have small to average size of breasts and why some have medium to large breasts.

Family Background 

One thing that has the biggest contribution to the size of your breasts is your mother’s and your grandmother’s size. Your genes have lots to do with your other characteristics, including the size of your breasts. 

However, do not just stick with this reason because it is not a guarantee that if your mom is a D cup, you’ll be like that, too. Your breast size can either be smaller or bigger depending on other factors.

Your Age

Your boobs may continue to grow or shrink depending on your age. Breasts start growing at puberty. Not all teens can have breasts at the same time. It depends on the maturity of your body and the amount of estrogen, a female hormone, you are producing. 

Your breasts can start growing at the age of 10 and end once you are 18 to 20 years old. As you get older, your breast tissues will begin to shrink because of tissue dehydration. Later on, your breast will sag and get smaller.

Body Weight

Changes in your body weight can also affect the size of your breasts. Your breasts are made up mostly of fat tissues. Therefore, the more fatty tissues you have, the greater chance you’ll have bigger breasts and vice versa. It will still depend on the type of body tissues that you have.

Your Period

Having menstruation means having more working hormones in your body. During your menstrual cycle, you may experience premenstrual syndrome (PMS) which includes pain in your lower abdomen and back, headaches, tender breasts that are painful to touch, and even mood swings.

These are all because of the change in the amount of estrogen and progesterone in your body. These hormones can stimulate milk ducts making your breasts tender and bigger. After your period, your breasts will return to their normal size and texture.

Pregnancy and Nursing

Pregnancy can cause an obvious size difference because of your body changes. The reason behind this is the preparation of your breasts to nurse a baby. Your milk ducts are getting more active and your body keeps on producing more. That is why your breasts feel heavier when you’re pregnant.Woman wearing a plaid longsleeved shirt over a black bralette

How to Determine Your Bra Size

Since not all breasts are created equal, then it is very important to measure them to get the right size of bra that you need. Having the right size can keep your breasts healthy and in shape. So here are the three parts that you should measure to know your size.

  • Measure the length around your torso. It is also called the band. 
  • Next is you have to measure the length across your breasts, which is commonly known as the bust. You can measure the band and the bust using a tape measure.
  • Lastly is to measure the cup or the volume of your breasts. You can do this by finding the difference between the band and the bust or using the tape measure as well. You may also use a sizing chart to guide you depending on which country you are in.

Related Questions

Are There Conditions Associated With Breast Size?

There are many conditions associated with your hormones and genes and not just your breast size alone. You can have cysts, mastitis or inflammation, and skin allergies which are also caused by a wrong bra. People with bigger breasts may also experience more tension and pain in the back, shoulders, and neck.

Is It Normal for My Breasts to Have Different Sizes and Weights?

It is normal for your breasts to have different sizes and weights. This happens because of hormonal imbalances and different growth rates. Uneven breasts can be embarrassing but there are solutions to that already. You can add padding or select a bra that is designed for uneven breast size.


Your boobs can be big as 34DD for an average size, or as small as an A cup. However, some women can have bigger or smaller breasts than that because of genetics, hormones, age, weight, and other factors. To properly take care of your breasts no matter the size, you should use a perfectly fitted bra to prevent pain and other disorders.


Hi there, I’m Allena, Founder and Editor of The Better Fit. I’ve always had a passion for finding ways to help women improve various areas of their lives. I have researched and worked to create this website so women would have a place to come and be informed about an article of clothing they literally wear every day.