There are a few specific qualities I look for when choosing a bra. Whether it's for a Leonisa shopper or for myself, my focus is always on the quality elements that make up a great bra, those details that guarantee a perfect fit and high performance. I look at factors like the material the cups and band are made of, straps (if there are any), overall bra style, level of padding, support, and cup size. When helping a client find her best bra, I shop within her style criteria and list of desired results using these criteria with special focus on the correct cup size.
I get questions about bras and cup sizes all the time, with questions ranging from specific styles and different types of cups to helping clients find a size that will fit regardless of bra style, material or band width. My answer to all these questions can be summed up like this: Your cup size is unique and it’s determined by your unique measurements, but different bra styles can fit differently, too.
If you find bra sizing confusing, know that you're not alone. I'm here to help you find the right cup size and band size that work best for you. To help explain this in detail, I’ve created this cup size comparison guide for sizes A-DD that also includes helpful tips for finding your overall best bra size and discovering your sister sizes. Let's get started, shall we?
It’ll only take 4 minutes.
Finding the Right Cup Size
When it comes to finding a bra, cup size isn’t something one merely estimates. It’s worth it to find your exact cup size according to the size chart of the brand you’re shopping, because an accurate cup size match helps your bras fit better. You’ve probably experienced a few annoying effects of wearing ill-fitting bras. These common bra issues might include red marks on your skin, spillage, skin bulges, gapping, wrinkles and more. What if I told you that all these problems can be solved by a change in your cup size? Simply changing this one factor can help you choose bras that offer a better fit, which can help you avoid the other problems I mentioned above.
What is a cup size?
Your cup size refers to the size of the cup, not any other part of the bra. Cup sizes start at A (or sometimes an AA or AAA), and move up alphabetically to B, C, D, and beyond. As the letter increases, the cups become deeper and wider. For example, someone with smaller breasts might fit best in A cups or B cups, while those with larger breasts might fill out C cups or D cups.
How is cup size measured?
To calculate your cup size, take your bust measurement (including the fullest part of the breasts) and subtract your rib cage measurement (underbust). Each letter corresponds with the number of inches from your measurement.
- 1 inch = A cup size
- 2 inches = B cup size
- 3 inches = C cup size
- 4 inches = D cup size
- 5 inches = DD cup size
Compare Cup Sizes: A vs. B Cup
Both A and B cup sizes make up the smaller end of the spectrum. Unlike bigger sizes, which often need extra support to prevent back pain, A and B cups have more flexibility. While not medically necessary for daily wear, many people with A or B size breasts choose to wear bras for coverage and smoothness under the clothes, to create a specific silhouette, or simply to feel more comfortable or “dressed.”
If your breasts fall into one of these smaller cup size categories, it's still important for you to wear a sports bra when working out or engaging in high-impact activity like running or jumping. Even A-cup boobs bounce during an intense exercise. Wearing a sports bra will keep you comfortable and help prevent long-term stretching of the ligaments in the chest area.
What does an A cup look like?
Do you think your cup size is an A or B? Grab your measuring tape to find out! If your bust measurement, which measures all the way around your rib cage including your breasts, minus your band measurement, which measures all the way around your rib cage just under your breasts, equals exactly or close to one inch, then your regular cup size is in the A category. If that measurement - called the cup size measurement - is closer to two inches, then you're in the B cup category.
What does a B cup look like?
It actually depends on the size of your band. The volume of the cup changes with the width of the chest. The wider the chest, the more breast tissue will have to spread across, appearing more flat or shallow. As a result, 32B, 34B, 36B are all different cup volumes, and you cannot just simply change the band size and keep the same cup size letter. See below how to calculate your correct bra sister size (it’s very helpful to know when you need to try a different band size to get the same cup volume!)
Best Bras for B Cups: B cups work well with just about any bra style – push up, wireless, strapless, demi, or full coverage. Leonisa sells a great variety of comfortable and sexy bras suitable for B cup breasts.
Comparing Cup Sizes: B vs. C Cup
As the list of cup size comparisons goes from A to DD or even beyond, consider the C cup to be the midway point of the scale. If your breasts fit best inside a bra with C cups, you have so many great options when it comes to bras and what they can do for you. Of course, this is not to say that their little sister, the B cup, doesn't have anything to offer. Let's compare.
A pair of B cup boobs is enough to show off and enhance, but they're also easily secured for a workout. If you're looking to take your B cups to the next level, look no further than a high push-up bra, which will visually take you from B to C - and maybe a little further - in no time.
For those of you who comfortably fill C cups without push-up power or other bra enhancements, know that there is no shortage of ways for you to wear a bra, either. Your size C cups might look best in a soft bra made of t-shirt fabric or a wireless bra, though a traditional underwire bra is a solid option for optimum support and shaping power.
Best Bra for C Cups: If you wear a C cup, we have great news! A C cup breast fills out nearly any bra style beautifully. Go for sexy bra styles with mesh cutouts, sleek fabrics, sultry color combinations and more.
Compare Cup Sizes: C vs. D and DD Cups
The difference between C and D cups can be surprising. I've found there is a bit of gray area between C cups and D cups, and that's mostly because the two cup sizes generally include those with similar band sizes. The distinction between D and DD cups can get even foggier (see bra sister sizes below for more information).
If C cups are the midpoint or medium breast size indicator on the cup size scale, then D cups mark the transition towards larger and fuller breasts and DD cups fall at the opposite end of the scale from A cups. You see, C cups are quite versatile and, like B cups, tend to fit nicely into a diverse selection of bra styles while still looking natural in shape and proportional to the body. On the other hand, to my ladies with lovely, large D cups or DD cups, you're blessed with the size that push-up bras were designed to emulate. Take care of them, support them and, if you choose, flaunt them!
Best Bra for D Cups: Larger cup sizes should be met with more support. For those with D cups, I recommend a supportive underwire bra to keep D cup size breasts lightly lifted and secure all day. Thankfully, Leonisa has extremely comfortable underwire bras in an impressive range of styles.
Best Bras for DD Cups: Underwire bras are a great everyday option for DD cups, too! In addition to having a few underwire styles in your bra rotation, I would like to recommend a minimizer bra for those times when you need a little extra support. These bras offer a smoothing effect around the cups, under the arms and in the back area for a seamless and sleek look underneath your clothing.
Bra Sister Sizes
If you remember, we talked about band size earlier and how, combined with the cup size, it customizes the fit and support level of your bra. The band size can also give you a bit of wiggle room in terms of cup size, and I see most of that happening between C, D, and DD cups. This “wiggle room” is also known as your bra sister size. Knowing your sister sizes comes in handy if your regular bra size isn't in stock or you want to try different cup and band size combinations for an even better fit.
To find your bra sister size, you just need to take your current size – let’s say it’s 36C – and choose either the band 34 for a tighter fit around the rib cage, or the band 38 for a more relaxed fit. Then, adjust the cup size to be one size bigger for a smaller band (34D) or one size smaller for a larger band (38B). It’s easy to remember: when you increase the band size, decrease the cup size, and when you decrease the band size, you need to increase the cup size.
Why do bra sister sizes work? Because the cup volume is an equation including both the cup size and the band size. A 34D bra will have cups with the same volume as a 32DD or a 36C bra. Cool, right?
Top Rated Bras
select colors + sizes
Bra Cup Styles
When choosing a bra, you will also want to take the cup style into consideration. Different cup styles offer a different level of coverage.
- Full cup bras (also called full coverage) provide the most coverage for ultimate support and comfort. They’re recommended for full busts because they support the weight of the breast. Many include underwire for even more support. They tend to have wider straps for support, but most of the support should come from the band of the bra. Full cup bras are an everyday go-to for C cup size, D cups, DD cups, and beyond. They work great under T-shirts, blouses, and dresses.
- Demi-cup bras (also called half-cup bras) cover the lower half of the bust. They have a triangular shape and just enough plunge to make them perfect for low-cut tops. Some of them have convertible straps that can be worn classic or crisscross in the back, letting you pair them with multiple shirt styles.
- Balconette bras offer a similar level of coverage to demi-cup bras, except the cups are rounded at the top and they can typically be worn strapless. Not only can they be worn with low-cut tops, but they can also be worn with sleeveless tops, or anything where you don’t want the straps to be sticking out.
- Push-up bras center and lift the bust with built-in push-up padding, also available across cup sizes.
Explore all the bra styles we offer at leonisa.com. We have a bra style for every day, every outfit, and every mood. They highlight your curves, they’re comfortable and supportive, and many of them even disappear under clothes! Just make a wish and find a bra with the features of your dreams.
Cup Size FAQ
Still have questions about your bra cup size? Don’t worry, we’ve got you covered.
The cup size is the letter portion of your overall bra size. For example, in 34B, the B is the cup size. Cup sizes include A cup, B cup, C cup, D cup, DD cup, and beyond!
Using a measuring tape, measure just under your bust for the band size, then measure around the fullest part of your bust. The difference in inches between the two determines your cup size. We offer guidance with pictures and video for you to find your bra size.
The letter reflects the difference in inches between your underbust and bust measurements. A cup boobs represent one inch difference between the underbust and bust sizes, B cups have a 2-inch difference, a C cup size represents a 3-inch difference, and so on.
You’ll know your bra’s cups are too tight if it creates a “quad boob” effect, with extra breast tissue spilling out from the top of the cups. It may look weird, but what’s even more important is that it will feel uncomfortable. Try going up a cup size but staying at the same band size - for example, if you’re spilling out of a 34B, try a 34C for a better fit and more comfortable feel.
A cup that’s too small will dig in and your boobs will spill out from the top. If the cups are too big, you’ll notice wrinkles or gapping. The perfect cup size is one that fits smoothly and supports comfortably. A cup breasts will be subject to gapping in a B cup bra, but D cup breasts will spill out of an A cup bra. Finding your cup size will help you find a bra that provides the support - and, most importantly, the comfort - that you’re looking for!
You can try both of the sizes you’re in between and see which one fits better. You may also want to opt for non-molded cups, like fabric cups, for a more flexible fit. Or you can consult with one of our Personal Shoppers!
It’s not unusual for bra cup sizes - or band sizes, for that matter - to change over time. If you’ve experienced pregnancy, weight loss, weight gain, hormonal shifts, or if you just feel like your bra isn’t fitting right, it’s good to re-measure yourself. We also recommend checking your bra size at least once a year just in case.
Yes! We have a full, easy-to-use size guide to help you find your ideal fit. Plus, our Personal Shoppers and our Customer Service team are eager to help you.
Our largest cup size is a DD cup, which is available in multiple styles that offer excellent support.
Our bras start at a B cup, but AA cup is typically recognized as the smallest size. Some specialty brands even offer AAA cups!
Leonisa Style Confidants are a team of personal shoppers and intimate apparel experts who help women find the perfect fit for their bodies and lifestyles. With experience in fashion, styling, and body-positive guidance, Susana, Laura, Alejandra, and Camila offer personalized advice on bras, shapewear, and everyday essentials. Through consultations and expert tips, they empower women to feel confident, comfortable, and supported in what they wear.
