Bra Size Guide (Sizes Explained)

USA to International Bra Size Converter Charts

It’s important to note that, just as with sizes for other clothing types, bra sizes are not always the same between countries. A US 32G and a UK 32G are very different! So it is crucial that you know which country’s sizing system the bra you are buying is using on its label.

How to Measure Your Bra Size

Whether you use the calculator, the chart, or want to work out your bra size yourself, you’ll need at least two key measurements – over and under your bust. Be sure to use inches, not centimeters. Here’s how to take the measurements accurately:

Underbust                                                                                                                    

Wrap the tape measure around your ribcage, where the crease below your breast is. Ensure it is horizontal all the way around the body, and pull it comfortably firm.

Overbust

Wrap the tape measure around the fullest part of your bust (usually over the nipples). Ensure it is horizontal all the way around the body and is not digging in at all.

How to Calculate Your Bra Size

To Bra size calculator yourself, simply follow these two steps:

Cup size: overbust minus underbust

The difference is how many cup sizes you’ll need to count up to, i.e. 1” difference is an A cup, 2” difference is a B cup, and so on.

Band size: underbust (+ 1 if odd)

Your underbust measurement in inches will be your band size. However, since odd band sizes don’t exist, you will need to add 1 to odd-numbered measurements.

Example

Let’s say your underbust measurement is 35” and your overbust measurement is 42”. That’s a 7” difference or a DDDD/G cup. Your underbust measurement is odd so you add 1, leading to a band size of 36. Your bra size is a US 36DDDD/G. You can check the bra sizes chart or calculator further up this page to confirm.

Why Is It So Hard to Find a Bra That Fits?

Do you struggle to find a list of bra sizes that fits? You wouldn’t be alone. These body-contoured garments require a much more precise fit than tops and dresses – if the design is out by as little as a few millimeters, it can noticeably affect the fit. Unsurprisingly then, there is little standardization between brands. One brand’s 32B won’t necessarily be exactly the same size as another’s 32B, which can make finding your perfect fit tricky.

Many people don’t even realize bra sizing goes beyond a DD, because that’s where major US retailers tend to stop. And stores have been known to incorrectly measure people as a DD because it’s the biggest size they have, and they want to make a sale. But as the bra size chart above shows, the largest cup size is much bigger!

How Should a Bra Fit? Bra Fitting Done Right

If you know how a bra is supposed to fit, you’ll be able to instantly tell if one doesn’t. Here are the three key things to check for:

The band – should be firm and horizontal

The band of the bra is responsible for around 80% of the support work, but it can’t do that if it’s allowed to slip and slide around. If it’s too loose, it will arch up at the back because the weight of your bust is pulling it down at the front (think of it like a see-saw). However, it also shouldn’t be so tight that it’s cutting in – you need to be able to take a deep breath when you want to!

The cups – should lie flush against the skin

If the cup size is too large, you won’t fill it out and the cup will gape or wrinkle. If it’s too small, your breast tissue won’t fit properly inside and will spill out somewhere – at the sides, at the front, or at the bottom. Check that the wires are sitting just below (not on top of) your breasts, and that when you view your bust from the side, there’s not a bump where the cup ends.

The straps – should not dig in or slip off

Your bra straps should always feel comfortable, and you should be able to easily slip a couple of fingers under them at the shoulder. When they dig in or are continually slipping down, it’s usually the case that the bra band is too big.

Why You Won’t Always Wear the Same Bra Size

And just when you thought you’d figured out your bra size, it turns out that we all have multiple ‘correct’ sizes! It’s actually completely normal to have bras in various sizes that all fit well, and one of the reasons for that is the size differences between brands that we mentioned above.

However, the bra style also affects the fit. You might need two different sizes from the same brand, if the bras are not the same style. For example, sports bras need an especially firm band to do their job correctly, so you might want to buy a band size smaller than your usual.

Plus, breasts come in different shapes as well as different sizes. If you have a lot of upper fullness, you may find that you spill out of a low-cut balconette cup, and need to go up a cup size compared to the one you wear in a tall, full-cup bra. Or conversely, if the upper half of your breasts is shallow, you may fill out the bottom of that full-cup bra just fine but not the top of it, and need to go down a cup size.

For this reason, it helps to know your ‘sister sizes’, explained below.

What is bra sister sizing?

Did you know that ‘D cups’ come in lots of sizes? The ones on a 44D bra will be much bigger than the ones on a 32D! For this reason, you shouldn’t swap just your cup or band size. You should change both.

For example, let’s assume you normally wear a 34C. You’ve just discovered a new brand, but the bands come up quite loose. So you try a 32C, right? Actually, no. Those 32C ‘C cups’ are smaller than the 34C ‘C cups’, so while this new band might fit just fine, the cups will now be too small.

When you move down a band size, you should also move up a cup size. And vice versa. And if you go down two band sizes? Then go up two cup sizes. This is called bra sister sizing.