Bra Size Calculator

bra fit calculator

All it takes is three quick measurements! Need more detailed directions? Everything is explained below.

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How To Measure Your Bra or Sports Bra Size

While bras and sports bras tend to be different in fabric and daily use, you can calculate their measurements in the same way in our calculator above which generate your recommended band and cup size. Then, depending on your activity and desired support based on size and activity impact level support, our proprietary T9 Barbell Rating system can help guide you in deciding which bra will provide you just the right support whether you’re running daily errands or jumping rope.

We've done our best to take out the guesswork and make finding your cup size and band size simple. Push-up bras and padding can skew things, so pull on a shelf bra camisole or your best fitting everyday bra and grab an inch tape measure.

  • Step 1: Measure around your chest, just under the arms and above the bust. Make sure that the tape measure is taut and is straight across your back, but not tight, or that could result in a squeeze later. Breathe out, relax your shoulders. We'll get through this together. If the measurement is an odd number or a half size, round it up to the next even number inch (for example, 33.5 will actually be 34). This number is known as your band size. Unsure you've got it right? Take a seat - our chests expand some when seated.
  • Step 2: Now it's time to measure your cup size. Take your bust measurement around the fullest point of your breast. This could be at the nipple, but everyone's breast shapes are different. This will be one of two measurements that you need to determine your cup size.
  • Step 3: For the final measurement, measure just under the breast around your ribcage.

Got the measurements? Good. It's time to calculate your bra size.

What you should know about measuring your bra or sports bra size

  • Women can experience upwards of nine major bra size changes in their lives, so it's a good idea to get sized at least once a year.
  • Whether you're shopping for an everyday bra or a sports bra, the size you wear is the same in both. No need to size down for more support!
  • Bras do eventually get worse for the wear due to all that washing. It's important for your girls that no sports bra ever celebrate a birthday!

Buying a sports bra and not sure where to begin? Our Sports Bra FAQ can help.


Prefer using a chart instead of a bra size calculator? Using the same measuring guidelines above, reference the chart below to find your cup size and band size.

What's my band size?

Measure above the bust, around your chest, just under the arms (Step 1 above).
Above Bust Measurement Band Size
29in - 31in 30
31in - 33in 32
33in - 35in 34
35in - 37in 36
37in - 39in 38
39in - 41in 40
41in - 43in 42
43in - 45in 44

What's my cup size?

First, measure around the fullest part of your bust (Step 2 above).

Next, measure around your rib cage, just beneath your breasts (Step 3 above). Deduct your rib cage measurement from your bust measurement in order to determine your recommended cup size (round up if between sizes.) Use the chart below to figure out your cup size!

If Bust Measurement Minus
Rib Cage Measurement Equals:
Then Cup Size Is:
1 inch AA
2 inches A
3 inches B
4 inches C
5 inches D
6 inches DD
7 inches E (DDD)
8 inches F (DDDD)
Bra Sizing FAQs

How do I calculate my bra size?

Calculating your bra size is easy. Before you take another online quiz or try to find your size from reading a chart, we'll teach you how to get your measurement and your bra size right. All you need is tape measure and a notepad or notes app to write down your measurements. To get the most accurate measurement possible, make sure you're wearing a non-padded bra. A padded bra adds volume to your bust shape that isn't naturally there, so go for a bralette with a wire. The wire will give just enough support to keep your breasts leveled while you measure.

Let's start with your bra band size. Grab your tape measure, and wrap it around the top of your ribcage, right underneath the breasts. Make sure the tape measure is snug around the torso. If the number you land on is an even number, add 4 inches to the measurement. If it's odd, add 5. Do a quick little addition, and boom, you've got your band size — don't forget this number! Double-check your bra band size is right by measuring around the top of your bust, right below your underarms.

Now let's find your cup size. Wrap the tape measure evenly around the fullest part of your bust. Try to keep the tape measure as leveled as possible. Write down the number you land on.

Your bra size is your band size subtracted by the cup size you just measured. So, let's say you measured 36 inches for your bust, and 34 inches for your band. That's 36 - 34 = 2 inches of difference, making you a 34B. One inch of difference would make you a 34A, three inches a 34C, and four inches 34D. Don't feel like doing the math? Add your measurements to our bra size calculator to get your bra size right.

Is DDD the same as F?

The short answer: yes! Here in the US, DDD is the same as F. But, if you were bra shopping in the UK, for example, DDD/F would be E. Some US-based brands don't always get this distinction right, and bra size charts aren't always consistent. But at Title Nine, we consider DDD and F to be the same.


How big is a cup D breast?

If you're measuring your bra size with a tape measure, a D cup is going to come out to 4 inches of difference from your band size. A D cup is not the same as DD cup or DDD cup. If you're a D cup and want a comfortable bra fit, easy support, and ideal coverage, you've got tons of options to choose from, from minimizer bras, to full coverage bras, to everyday bras that fit and feel like your favorite sports bra.


What is the bra +4 method? Why do you add 4 inches to your band size?

You'll only need to add 4 inches to your band size if you're measuring with a tape measure and it lands on an even number when wrapped around your ribcage.


Is it better to go up a cup size or band size?

That all depends on the bra fit you're going for. Obviously, you want to be comfortable, but sometimes we need to do a little band and cup size hacking to get the best fit possible. Your cup size is influenced by your band measurement, so if the band changes, so does the cup. That said, it's not necessarily better to go up a cup size over band size, and vice versa. It's all relative—when one changes, so does the other. If you're happy with your cup fit but want a bit of a looser fit around the band, size up on the band. If your cup fit is too snug but the band feels just right, go up one cup size.


Is it better to size up or down in bras?

Whether it's a sports bra or an everyday bra, sizing up or down isn't the move. The key is to get your size just right so you get the support you need without sacrificing comfort. There are some exceptions, though. If you're in the middle of weight loss, weight gain, pregnancy, or post-partum, and you're preparing to fit into a new bra size, then sizing down or up would be OK in this case. We suggest waiting on this, though—you don't want your breasts to be squished or floating around in your bra.


How do you tell if your cup size is too big or small?

Sometimes you don't need to look at a chart to know your bra isn't fitting right. There are some easy tell-tale signs of a poor-fitting bra.

Your cup size is too big if...

  • There's extra space between your breast and the cup (AKA a cup gap)

  • You don't feel supported by your bra

  • You're constantly readjusting your bra

  • You've tightened the adjustable straps to compensate for the cup gaps

Your cup size is too small if...

  • Your breasts are spilling out of the cups

  • You've got side boob—another sign the cup isn't covering the whole breast

  • The underwire is poking you

  • You have red marks on your breasts after taking your bra off

  • Your breasts are squished together at the center of your chest


Why does my bra get tighter as the day goes on?

It's totally normal for your bra to feel tighter by the end of the day. It all comes down to the natural fluctuations and hormonal changes women go through every single day. Our breasts, and therefore our bust size, can either shrink or swell up morning to night for a number of reasons: water intake, exercise, breastfeeding, and more.


What is the difference between DD and DDD?

DD and DDD cups are two completely different cup sizes. DD will have 5 inches of difference from your band size, and DDD will have 6 inches of difference. DDD is also often recognized as an F cup.


Why does my bra ride up in front when I lift my arms?

If your bra rides up in the front, this is another sign you're wearing the wrong size. It's likely that the band is too loose, and you need to size down to a more snug fit that keeps your bra in place.


How tight should a bra be?

A bra should fit not too tight, not too loose, but just right. A nice and snug fit on the band and comfortable fit on the cups is a pretty good tell that you've got your fit just right.


Why do my bra straps keep slipping off my shoulders?

If you find yourself constantly pulling your straps up and back in place, it might be time to replace your bra. It could also be a sign that you're wearing the wrong size bra altogether. If the adjustable straps can't be tightened anymore and still slip off, the fabric has reached its limit and won't stay in place.


Why does cup size increase with band size?

Cup size will always change with the band size. This is because the measurement of your band influences your cup size.


What happens when you go up a band size?

If you go up a band size, you'll likely have to go down a cup size to compensate the difference. To be totally sure, though, measure yourself again either with a tape measure or fit expert.


contributing T9 bra Expert

Molly Hanks, Merchant

Mom, competitor, triathlete and adventure trail runner, Molly has been the resident Bra Expert at Title Nine. She not only leads and manages wear testing across the entire line, but also works with our in-house product development team and women across the industry to uncover and adopt the features most important to us in bras regardless of your cup size or activity.

Bra Size Calculator & Bra Size Chart

Wondering what bra size you are? Title Nine's bra size calculator has you covered. T9 will help you learn about sports bra sizing and how to measure for the right comfort and fit. From AA to DDD Title Nine's bra size calculator will help you find the right bra that will have you feeling strong and confident throughout the day. Check out T9's bra fitting guide to help find the right fitting sports bra to keep you in the game.