How to measure your bra size

Bras are the unsung hero of a perfect outfit. When properly fitted, they can enhance your silhouette, provide support and lift, and even help with posture and back pain. Of course, finding the perfect fitting bra isn’t always a straightforward process. Bodies fluctuate, and sizing can be inconsistent across different brands and styles. 

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If you’re confused on how to measure your bra size, you’re not alone. As opposed to clothing sizes, which generally become larger as the sizes increase, bra sizing attempts to take many different factors, like breast shape, breast size, and band size, into account. While this can result in a more custom-feeling fit, it can also take a bit more effort to determine your best size.

That said, don’t let the extra steps intimidate you. We promise if you trust the process, you will be rewarded with a perfect fitting bra. After all, there are reports that say 80% of women are wearing the incorrect bra size, and that’s simply no way to live your life. We’ve broken it all down into an easy step-by-step guide to help you find your perfect fit.

Download our step-by-step bra size calculation worksheet here.

How is bra size calculated?

Each bra size features a letter and an even number. The letter refers to your cup size, and the number refers to your band size. Cup sizes start at AA and go all the way up to K, getting larger as you go further down the alphabet.

It’s a common misconception that your band size is equal to the measurement of your under bust. While that number will be necessary in order to calculate your final bra size, you cannot simply measure your band to get your final band size. Don’t fear — we’ll walk you through the simple math you’ll need to do to get your final band size. 

Finding your bra size

Step one: Find a measuring tool

First, you will need something to help you measure. The best tool for the job is a long, soft measuring tape. If you don’t have one on hand, you can use a piece of string or ribbon instead. If you’re using string or ribbon, you’ll mark the length of your measurement with a marker or piece of tape, then use a ruler or hard measuring tape to measure the length of the string or ribbon to the dot.

Step two: Dress accordingly 

Before you begin taking your measurements, make sure you’re wearing a non-padded, underwire bra. Any bra that has too much padding in the cups will produce the wrong measurements, and any bra that features compression of any kind, like a sports bra, will also give you an inaccurate result.

Step three: Find your band size

We’ll start by figuring out your band size. Measure directly underneath your bust, where your bra band would sit. The tape should be level and snug. Round your measurement to the nearest whole number, then use the chart below to calculate your band size.

MEASUREMENT IN INCHES	HOW TO CALCULATE BAND SIZE
26 - 32	If even, add 4. If odd, add 5
33 - 38	If even, add 2. If odd, add 3
39+	If even, add 0. If odd, add 1

 

For example, if your band measurement is 30, you would add 4 to get a 34 band size.

 

Step four: Find your cup size

Now, onto cup size. Pull the measuring tape somewhat loosely around the fullest part of your chest and round to the nearest whole number. Make sure the tape is straight across your back. 

For our example, let’s say our bust measurement is 35.

Remember your original band measurement? Locate that number you wrote down and add 2. In the example, our measurement was 30, so we would add 2 to get a 32 calculated bust measurement. Now, subtract that number from the bust measurement we just got. Based on the example, that would mean 35-32, leaving you with 3.

Using the chart below, you can determine your cup size. 3 equals C. Add that to your calculated band size (in the example, that would be 34), and we’re left with a final bra size of 34C.

 

The difference (in inches):	Your cup size is:
1	AA
2	A
3	B
4	C
5	D
6	DDD, F
7	G

Sister sizing

Numbers tell one thing, but it doesn’t always capture the unique shape of your body. Remember, this is an art, not a science — you have to try bras on and experiment with sizing and styles. If you’ve done your measurements correctly and you’re still not getting a perfect fit, try a sister size. 

What is a sister size?

Because the cup and band system produces so many sizing combinations, there are usually several sizes that are very similar in size and fit. These are known as sister sizes. 

How do you find your bra’s sister size?

• Go up in cup size and come down in band size
• Go up in band size but down in cup size

Which size should I try?

If you’re on the bustier side and have a lot of fullness is in the front, try a smaller band with a bigger cup. if you carry more around the sides of your body and back and you aren't as full in the cup, try a  bigger band with a smaller cup. 

For example, if you first tried a 34D but it didn’t fit quite right, you might try a 36C or a 32DD. Both of these are sister sizes to 34D.

Additional tips to find your perfect fit

Why is my bra size different depending on bra style?

Your size may vary from style to style. For example, you might be a 34C in a standard underwire t-shirt bra but need to size up to a 34D to fit in a plunge bra. When you’re experimenting with new bra styles, be prepared to try multiple sizes to get your perfect fit. Check out our complete guide to popular bra styles here.

What if my breasts are different sizes?

If your breasts are two different sizes, you’ll most likely be more comfortable wearing the size that fits your smaller breast.

Bra fitting

How can I tell if my bra fits properly?

• The band of the bra should be level all the way around your body
• Your breasts should fill the cup without spilling over
• The straps should stay on your shoulders without digging in
• The center of the bra lays flat against your chest between your breasts
• Your bra is so comfortable, you forget you’re wearing it

What are some signs my bra doesn’t fit?

• Your breasts don’t fill the cups, leaving gaps of space or wrinkling in the cups
• Your breasts spill out over the cups, creating an indent in your silhouette
• You can feel underwire pinching your skin
• You see red marks on your skin after you take your bra off
• You don’t feel secure or supported
• You feel any pain or discomfort while wearing your bra

Sometimes you may be wearing the proper bra size, but you just need to make a few adjustments to get your perfect bra fit. Here are some tips to help you customize your fit. 

• If the band in the back has multiple rows of hooks and eyes, make sure you hook your bra at a level that is tight enough to provide support, but loose enough to prevent digging in or bulging. You should be able to slide just one finger beneath the band. 
• If your straps are slipping off your shoulders or you feel like your breasts need additional support, try tightening your straps. Some bras give you the option to cross your straps in the back, which can also increase your level of support.
• If your straps are digging in or your band is riding up in the back, try loosening your straps.

If you still need help finding your perfect fit, you can learn more about finding your correct size based on your fit issues here. 

When should I take my measurements?

Your bra doesn’t pass the fit test. 

Did you read the fit section above and come to the realization that your bra is not a perfect fit? Don’t worry, it’s incredibly common — most women are wearing the incorrect bra size. But, that’s no reason to settle for bad support. 

When you change in size. 

The only thing that’s certain about bodies is that they will change. Whether you experience a major life event like childbirth, or you go up and down in weight for any other reason, your bust size is likely to change, too. If you’ve noticed any recent changes to your body, it’s always smart to take another bra measurement and consider if there’s a better fit out there. 

When it’s been a while

We recommend measuring yourself at least once a year to ensure you're still getting the best fit for you.

FAQs

What should I do if my breasts don’t fill the cups and there’s gapping or wrinkling?

Typically the solution for this problem would be to go down a cup size, but another aspect to consider is the style of the bra. For example, if you have fuller breasts, a full coverage cup may be a good fit. If your breasts are more tear drop shaped, for example, you might be more comfortable in a demi cup or balconette bra. Read our guide to bra styles here. Lastly, you may also want to consider a push-up bra with light padding that can help fill in the gaps. 

What should I do if I’m spilling out over the cups?

You might find that your breasts spill out over the cups, creating bulging in the front of your neckline and on the sides of your chest. If this happens to you consistently, look for bras that are specifically created for fuller-busted women or try a t-shirt bra style.

What should I do if my band keeps riding up?

This most likely means your bottom band is too loose and you need to try a tighter row of hooks. If you’re already at the tightest level, you need a smaller band size. You can also try adjusting your straps and making sure that your underwire is sitting flush against your body.