How Big Is a 30C Bra Cup Size?

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A wrong-sized bra can lead to a world of pain and discomfort. The good news is that if you have come across this article, you are on the right track to finding your perfect bra size. Below I elaborate on how big is 30C and why it is considered an uncommon bra size.     

How Big Is 30C?

A 30C bra size refers to a band measurement of 30 inches and a bust measurement of 33 inches. As apparent, bra sizes are denoted by a number, which refers to the band size, and an alphabet, which refers to the cup size. 

Graphic image of a woman wearing a green tank top and black shorts while the word text around her states that a 30C bra size has a bust size range of 32-33 inches and a band size of 29-30 inches

Basically, the cup size is the difference between the band size and the bust size. Therefore, a C cup size does not automatically mean that you have small or big breasts. You also have to take the band size and your overall frame into account. 

To ensure that you buy a perfectly-sized bra, measure your band size and bust size:

  1. Begin by measuring your band size.  
  2. Wrap a measuring tape around your torso, just below your bust, where you would wear a bra band.
  3. Make sure that the tape is snug and level around your body.
  4. Note the reading.
  5. Next, place the boob tape around the fullest part of your bust, across your nipples.
  6. Make sure that the tape is loose and not pressing down on your nipples.
  7. Note the reading and subtract it from the band size to determine your cup size.   

30C Bra Size Details

30C SizeDetails
Band Size29 to 30 inches
Bust Size32 to 33 inches
WeightAround 1.72 pounds
Sister Size Up28D
Sister Size Down32B

Clothing Choices for 30C Breasts

Finding flattering clothing for a 30C breast size isn’t exactly simple. This body and breast type features a very slender frame with average sized boobs.

However, those average size boobs will probably appear pretty sizable on a small, petite frame. Here are some good clothing options to keep in mind:

For petite women with average sized breasts, like a 30C, having a great, everyday bra is essential. My #1 recommended t-shirt bra is the Calvin Klein Perfectly Fit T-Shirt Bra. It was voted “Top T-Shirt Bra” by New York Magazine!

Is 30C an Uncommon Bra Size?

30C is an uncommon bra size. A 30-inch band size means that you are petite with a very slender figure. On the other hand, a C cup size denotes a breast protrusion of 3 inches from your chest. This makes for a larger looking chest.

Woman in bed wearing a blue bra and leggings

Thus, if you fit into a 30C bra size, your boobs may look above average in size compared to your overall small frame.

Consequently, it is not very common to find a C cup size in smaller band sizes, as most brands only cater to the more popular selling sizes.     

What Other Bra Sizes Can Fit Me?

Research shows that almost 80% of women wear the wrong bra size, leading to discomfort. It is not surprising that I take off my bras as soon as I reach home.

Therefore, if you have trouble finding your 30C bra size, consider going for one of the “sister sizes.” 

Graphic image that features an illustration of three white dummies representing the sister sizes for a 30C cup size

The term refers to bra sizes that have equal cup volumes. You can find out your sister size by going up a band size while simultaneously going down a cup size. People with 30C bra size will fit into 28D, 32B, and 34A. Try each of the bras to see which one fits most perfectly.

Most often, 28 inches might feel too tight as it is a very small band size. You may have more success and a higher comfort level with 32B or 34A. For maximum comfort, you can try wearing unlined bras, or bralettes.

Related Questions

How Will I Know if I have a 30C Bra Size?

You’ll know you have a 30C bra size if your bust measurement ranges from 32 to 33 inches and the band measures around 29 to 30 inches. You must wear C cups if there’s a three-inch difference between the bust and band measurements.

What Are the Best Bra Styles for a 30C Size?

The best bra styles for a 30C include balconette bras, strapless bras, and boob tape. C cups are average in size, so you can choose between bras that prioritize support or those than shape the bust.

How Can I Make My 30C Size Look Bigger?

You can make your 30C bust look bigger by wearing contoured cups that push breast tissue up and center. You may also consider wearing padded bras to add bust volume.

Bra Size Measurement & Cup Size | A, B, C, D, DD Bra Sizes AND Extra Large Breasts


A 30C bra size has a band size of 30 inches and a bust size of 33 inches. This bra size is not very common since most women with a C cup size have wider torsos. As a result, you may have trouble finding this size. Regardless, you can always go for one of the sister sizes, which include 28D, 32B, or 34A.   


Allena is the Founder and Editor of The Better Fit, a platform dedicated to empowering women with practical advice on bras and fitness, inspired by her own revelation of the widespread issue of incorrect bra sizing. Her expertise and tips have been recognized by major publications such as Cosmopolitan, Better Homes & Gardens, Insider, and NBC, making her a trusted voice in women's wellness and lifestyle.