Bra sizing can be incredibly confusing, so we're going to walk you through what the numbers and letters mean and how to figure out corresponding sizes. Once you understand how bra sizing works, it will make finding a bra that fits so much easier!  This topic is SO IMPORTANT! This is going to change your world!  Let’s get started.

Number = Band Size

The number in the bra size is your brand size. Finding your band size is really easy. All you have to do is take a soft measuring tape and measure the base of your breasts or underbust. You want the measuring tape to be snug and not loose when measuring. Once you have your measurement round it up to the nearest WHOLE number and that’s your band size. There is a chart below that shows you the corresponding underbust measurements with the band size.

Bra Band Facts

Here are some important facts about your band. Your band is where 90% of your breast support comes from, so it’s VERY VERY VERY IMPORTANT that your band is fitting correctly. What I mean by fitting “correctly” is that it should fit snug on the loosest set of hooks when you first try it on. The reason you want the band to be snug on the loosest set of hooks is so you can tighten the band as it stretches out. The other reason is the bra will fit you longer.

When you buy a correct fitting bra, it’s going to feel quite snug at first. Don’t worry, it won’t be like that forever. It will take a couple of days of wear for the band to ease a bit.  

When trying on bras, if you have to hook the back to the tightest set of hooks for it to be snug, you need to go down a band size or try on a different bra. Some bras have stretchier material in the band then others.  

There’s two tests you can do to see if your band is fitting correctly.

The first is to put the bra on and move your arms around and jump up and down. When you’re done and if your bra hasn’t moved or if you don’t have to adjust the girls or pull it down, it’s snug enough.

The second test requires you have a partner on hand. Have your child, husband, friend, or a bra fitter try to slide their hand between the band and your back. If they struggle to do this, then your band is snug enough.

Every woman is different, but I like my bras really snug and there’s a couple reasons why:

First, I like my bras to last longer. If I’m going to spend my hard earned cash on a bra, I want it to last me as long as it can.

Second, I like the extra support.

Third, I love the feeling that my bra doesn’t move when I move.  I HATE the feeling of having to adjust my bra throughout the day. I don’t have the time or the energy to worry if I’m going to be falling out of my bra. I want my bras to do the work of supporting me and holding me in place. Sometimes I’ll go down a band size in some bras so I can get more use out of the bra. 

When you go down a band size you HAVE to go up a cup size to compensate the difference. I’ll explain this more in detail in the cup size portion of this post. I wouldn’t recommend this to every woman. Some women might not find this comfortable or feel like they need to, depending on the person, their needs, or what size they are. I sometimes recommend this to busty gals when they’re in need of more support or in need of more selection in bras.

“Back Fat”

This model doesn’t have much “back fat”, but I wanted to show you an example.

One complaint I hear from women who start wearing the correct fitting bra is back fat. Women don’t like the way the band is snug and it “squishes” excess skin on top and out of the sides of their back.

My thoughts on this are 99% of women have some type of “back fat,” even very thin and athletic women. Men and women are not going to be looking at your back, people are going to be looking at your bosoms. I’d rather have a little “back fat” then not have my boobs supported and therefore look heavier in the front.

If you want to look slender and supported, the key is wearing the correct band size and making sure it’s snug because the band is the foundation of the bra and that is where you get your support from. I like to compare your bra band to the foundation of a house.  If the foundation of your house isn’t strong (if your band isn’t snug), the foundation won’t be able to support the rest of the house (your boobs).  

I found a some great examples of how wearing a correct fitting bra can make you look slimmer in the front.

photo source

Look at what a difference not wearing the right bra size looks like on the left compared to the correct fitting one on the right. You can tell a huge difference! She looks like she lost at least 10 pounds on the right side picture. Wearing the correct band size is crucial for all women. Having a large bust can make you look heavier if you’re not wearing the correct bra size. Like I said above, I’d rather have “back fat” than have my boobs not look supported and therefore making me look heavier.

Letter = Cup Size

The second part to bra sizing is the cup size. The letter represents the cup size. The cup size is the trickiest part of bra fitting and takes the most time to figure out. But if you follow my tips, you’ll be able to do it without any problems.

There are two ways you can figure out your cup size. I prefer one over the other, but I’m going to go through how to do both of them so you can get an idea of what size you are. By having an idea as to what size you are, you’ll be able to spend less time hunting down a bra that fits. You’ll be able to tell the bra fitter at the department store what size you measure so you can give her a good starting point. If you get a really good bra fitter (like myself), I can tell what bra size you should be wearing just by looking at you.

The first way to find your cup size is to measure your band size (around your body right beneath your breasts) and measure the fullest part of the bust (bra on and shirt off). Subtract your band measurement from your cup measurement. For each inch in difference, the cup goes up by one size. Take that difference and check the chart below.

For an example, my band size measurement is 29 inches which equals to a 30 sized band. My bust measurement is 34 inches.  I’m going to subtract my bust measurement from my band size. 34-30=4  If you look at the chart above it says I should be wearing a D cup.

The second way to find your cup size is going to a department store or lingerie boutique that specializes in bra fitting. This is the most precise way to get a good fit. If you’re not sure where to go I would Google some local places, call them up and ask them the following: what range of sizes do they carry, are their fitters certified, do they specialize in fitting, and what bra brands do they carry?  It’s also good to ask what their return policy is, just in case you don’t end up liking the bra.  A good place should carry band or have access to sizes from a 28-52 and cup sizes from AA-J.

The brands I like the most are Chantelle, Calvin Klein, Cleo, Elomi, Freya, Natori, La Perla, Panache, and Wacoal.

I don’t recommend going to Victoria’s Secret to get fitted, go here to read why.

It’s worth it to invest in your bras.  Invest the time and energy to getting fitted correctly and buying the correct fitting bra.  You wear your bra EVERYDAY.  It will make you look thinner, your clothes will fit you better, and you will feel more comfortable.

Corresponding Sizes

The last thing I’m going to go over in this post is really important.  I think everything on this post is important, but this will help you to manipulate the sizing chart and therefore, make you feel like a rockstar because you understand what happens to your size when you go up and down cup and band sizes.  Also, by understanding this part, this can help you determine your size.

Another important part to understanding how sizing works is how there’s corresponding bra sizes.  Did you know a 32C and a 34B are actually the same cup size?  The only difference between these two sizes is their band size, the 34 is larger than the 32.  

In the chart below, there’s a highlighted column below you can see how all each column are the same cup sizes, but have different band sizes.  A 28DD has the same cup size as a 38AA.  So when someone says they’re a C cup, that doesn’t really mean anything without a the band size in front of it.  

There’s two really important things to remember when it comes to corresponding sizes.  

First, the larger the band size the larger the cup sizes are, and the smaller the band size the smaller the cup sizes will be.  You can be a large 38C or you could be a small 32C.  The C cups in a 38 and 32 are not the same.  A 38C cup size is three cup sizes larger than the 32C cup size.  For every band size you go up, the cup size goes up too.  

Second, whenever you go down a band size you HAVE to go up one cup size to compensate the difference.  If you go up a band size you HAVE to go down a cup size to compensate the difference. 

So let’s pretend you wear a 34C and you gained weight and your 34 band is too tight and is uncomfortable. Your cup size hasn’t changed, so you want to go up a band size, because you went up a band size you need to go down a cup size.  Or you could look at the chart above see that the corresponding size to the 34C is a 36B.

Bra Fitting

Now we’re ready to start putting our new bra knowledge to work.  This is “Friend A” below.

“Friend A” is wearing a 36B in the bra above. The arrows are pointing to her breast tissue that was hanging out of the top of the cup.  This means the cup size is too small.  After measuring “Friend A” for her band size she measured 31″ around.  I put her in a 32 band size which is two band sizes smaller than the 36 band she was wearing, I have to go up two cup sizes.

Let me repeat that one more time. So “Friend A” ended up wearing a 32DD.

She is wearing the Natori Demi Bra (the bra she is wearing is no longer being made, this one is the sister bra).  What a hot mama.

Here is the before and after.  You can tell she’s being covered correctly, the underwire isn’t sitting on top of her breast, the center of the bra is lying completely flat against her skin, and the band is low and snug in the back.

“Friend B” was wearing a 34C in the picture below.  You can see from the arrows this bra was way too small in the cup size.  From the arrows you can tell her breast tissue is hanging out at the top and side of her bra.  After measuring her around the top of her ribs she measured 27″ around.  The 27″ means she should be wearing a 28 band size.  Because we needed to go down two band sizes we had to up two cup sizes.

I had her try on 28DD and it fit her perfectly!  See how much better she looks in a correct fitting bra!  She’s wearing the

Calvin Klein Women’s Seductive Comfort Customized Lift Bra

I personally wear this bra and love it.  It’s reasonably priced, comfortable, and gives a subtle uplift.

Here is the before and after up close.  The reason why the Calvin Klein bra fits her so well is because it’s covering on the sides and front, the underwire isn’t laying on top of her breast tissue, the band is low and snug in the back, and she looks great.

I hope this post was helpful to about how bra sizing works.  It can be confusing so hopefully you were able to get a better understanding.  If you have any questions, feel free to leave a comment below.  

Click the images below to learn more about my in-person and online bra fitting services!






September 23, 2013 — Courtney