Full Bust Guide – What Large Cup Sizes Really Look Like
There’s a lot of misinformation out there about big busts and bra sizes. Even what society thinks of as ‘big breasts’ and what the lingerie industry actually counts as a full-bust size can be quite different!
Did you know for example that:
- The number in a bra size doesn’t say anything about the size of the breasts?
- The largest bra size is well beyond a DD cup?
- ‘DD’ isn’t even a specific size, since a 34DD person has larger boobs than a 32DD person?
This article explores everything from how big each cup size actually is to which bras are best for big busts. Read on to learn the truth about having and shopping for big breasts!
How does cup sizing work?
A bra size contains a number and letter. Only the letter – aka ‘cup size’ – relates to the breast size, while the number indicates the size of the ribcage below.
Cup size is measured as the difference between the ribcage and around-the-bust measurements. In other words, it tells you how far out the breasts stick from the body. Every 1” of difference equals one cup size – A = 1”, B = 2”, etc. Anything above a D cup is counted as a ‘full bust’ by lingerie brands.
However, what cup size doesn’t tell you is how wide the breasts are. A 40F wearer will have much larger boobs than a 30F wearer, because the 40F wearer has a wider body and hence wider boobs.
What is the largest bust size?
Theoretically, there’s no limit to how large cup sizes get can. But in practice, the biggest bra size you can find easily online is a US I cup, and the largest bra size you’ll find with some effort is around a US O cup.
Beyond that, for exceptionally large cup boobs, you may need to look into getting custom bras made.
What causes large breasts?
Often, bigger busts are simply the result of genetics. If other women in your family have large boobs, chances are you will too.
However, certain medications, thyroid conditions, weight gain due to the menopause, and weight gain in general can all cause your bust to expand too.
Plus of course, pregnancy! Your bra size will fluctuate throughout your life, but most women will experience their largest bust size while nursing. The breasts are plumped up with milk, which also makes them extra heavy!
Pros and Cons of Bigger Busts
Some full-busted women view their chest as a blessing. Others see it as a curse. It all depends on your viewpoint:
|Beauty – for better or worse, our society prizes large breasts as being attractive||Unwanted attention – especially from men, but even women may assume you are ‘flaunting’ your chest when it just looks that way in any outfit|
|Confidence – linked to the above, a large bust can make you feel sexier and hence more confident||Pain – your back especially can tire from supporting all that weight|
|Portable storage – okay, a bit of a jokey one, but all full-busted women have used their cleavage as a pen holder at some point!||Plainer, more expensive bras – it’s undeniably harder to find stylish bras in large cup sizes. They are also harder to design and make, so tend to cost more|
Now, time to learn about each larger bust size individually:
Large Boob Cup Sizes:
E Cup Breasts
What is an E cup breast size?
A US E cup size means that the overbust measurement (the fullest part of the breasts) is 5” larger than the underbust (ribcage) measurement.
How big is an E cup?
E cup boobs stick out around 5” from the ribcage. However, E cups on larger band sizes are larger overall, as they are wider.
Example E cup measurements
30” underbust + 35” overbust = 30E
34” underbust + 39” overbust = 34E
37” underbust + 42” overbust = 38E
What do E cup breasts look like?
How big E cup boobs look, and how much space is inside the cups of E cup bras, depends on the band size. Below is a comparison image of a US 30E (left) and US 36E (right):
Is an E cup the same as a DD, or is DD bigger/smaller?
E cups vs DD in America: In the US, E and DD are just different names for the same cup size. Some brands prefer a D-E-F sizing system, while others prefer a D-DD-DDD one.
E cups vs DD in the UK and Australia: Here, an E cup is one size larger than a DD, since the sizing system goes D-DD-E.
E cup sister sizes
The two E cup sister sizes are D (when you go up one band size) and F/DDD (when you go down one band size).
For example, the sister sizes of 34E are 36D and 32F/DDD.
Best bras for E cup breasts
E cups are a full-bust size, but one of the smaller ones. Therefore, they don’t always need bras designed for heavy-duty support, especially on the smaller band sizes.
Here are two popular E cup bras:
- Belle Floral Lace Balcony Bra by Fantasie (available in US 30-42E)
- Plus-Size Cate Underwire Full Cup Banded Bra by Elomi (available in US 34-46E)
F Cup Breasts
What is an F cup size?
In the US, an F cup size indicates that the overbust measurement is 6” larger than the underbust one.
Example F cup measurements
30” underbust + 36” overbust = 30F
35” underbust + 41” overbust = 36F
42” underbust + 48” overbust = 42E
Here are two examples of F cup breasts on different band sizes – a US 30F (left) and US 36F (right):
Is a DDD the same as an F?
F cups vs DDD in America: Again, due to the two sizing systems in the US (D-E-F vs. D-DD-DDD), these are just different labels for the same thing.
F cups vs DDD in the UK and Australia: In these countries, there is no such thing as a DDD cup size. However, their F cup bras are one size bigger than a US F cup (so are equivalent to a US DDDD cup).
What is the difference between F and FF cup breasts?
Firstly, an FF cup size does not exist in the US. There, the only letter that gets doubled (and tripled, and quadrupled…) is a D. It also doesn’t exist in mainland Europe, since they do not use any double-letter sizes.
FF is a UK/Australian size. It’s one size larger than their F cup size, and one size smaller than their G cup size. The US equivalent of a FF cup would be an H or DDDDD.
What is the difference between FF and G cups, are they the same?
As explained above, UK/Australian double letters sit between the single version of that letter, and the following letter in the alphabet. So no, FF and G cups are not the same – the G is one size larger.
F cup sister sizes
The F cup sister sizes are E/DD (when you go up one band size) and G/DDDD (when you go down one band size).
For example, the sister sizes of 30F are 32E/DD and 28G/DDDD.
Best bras for F cup boobs
Like E cups, F cup breasts are one of the smaller full-bust sizes. Therefore, F cup bras with only minimal tweaks for added support are often sufficient. For example, horizontal and vertical seaming that divides the cup into 3 sections (known as ‘3 part cup’ bras).
Here are two great bras for F cup boobs:
- Top Comfort Clara Soft Cup Bra by Anita (available in 34-48F)
- Ultimate Glamour Strapless Everyday Bra by Wonderbra (available in 30-38F)
- Plus-Size Cate Underwire Full Cup Banded Bra by Elomi (available in US 34-46F)
- Plus-Size Amelia Band Less Underwire Spacer Molded Bra by Elomi (available in US 36-46F)
G Cup Breasts
What is a G cup size?
In US bra sizing, a G cup size means that the person’s overbust measurement is 7” larger than their underbust one.
Example G cup measurements
26” underbust + 33” overbust = 26G
31” underbust + 38” overbust = 32G
40” underbust + 47” overbust = 40G
Here are examples of G cup breasts on two different band sizes – a US 30G (left) and 36G (right):
Is cup size GG bigger than G?
Yes, a GG is one size larger than a G. However, this is only the case in the UK and Australia, since GG doesn’t exist as a cup size in the US. There, the next size after a G is an H.
What is the difference between a G cup and a FF?
G cup vs FF in the UK/Australia: A FF is one size smaller than a G.
G cup vs FF in the US: FF is another size that doesn’t exist in the US. However, its equivalent would be a US H cup. In other words, it would be one size larger than a US G cup.
Check out the international cup size conversion chart on this page if you’re confused!
What do G cup breasts weigh?
The weight of G cup breasts varies, since their size does. G cup boobs all ‘project’ the same amount, but on a smaller band size they are narrower, and therefore smaller overall.
According to Hourglass Lingerie:
- 28G breasts weigh about 1.2lbs each
- 30G breasts weigh about 1.5lbs each
- 32G breasts weigh about 1.7lbs each
- 34G breasts weigh about 2lbs each
They also explain how to measure yourself using the ‘water displacement’ technique, if you want to know exactly what your own G cup boobs weigh!
G cup sister sizes
The G cup sister sizes are F/DDD (when you go up one band size) and H (when you go down one band size).
For example, the sister sizes of 40G are 42F/DDD and 38H.
Best bras for G cup breasts
Although smaller full-bust sizes can sometimes get away with wearing ‘regular’ bras, a US G cup is around the breast size where you will definitely need to look for bras with at least a few supportive elements. For example, look for G cup bras with wider bands, wider straps, and/or 3-part cups.
Here are two G cup bras we recommend:
- Morgan Banded Underwire Stretch Lace Bra by Elomi (available in US 34-44G)
- Plus-Size Cate Underwire Full Cup Banded Bra by Elomi (available in US 34-46G)
H Cup Breasts
What is an H cup size?
A US H cup size means that your overbust measurement is 8” larger than your underbust one.
Example H cup measurements
27” underbust + 35” overbust = 28H
30” underbust + 38” overbust = 30H
42” underbust + 50” overbust = 42H
Here’s a side-by-side comparison of H cup breasts on two different band sizes – a US 30H (left) and 36H (right):
Is H cup big?
Yes is the simple answer. Full-bust sizing begins at a US E cup (though some full-bust brands start from a D), so an H is well into full-bust territory. H cup boobs vary in size depending on the band size (e.g. 40H is bigger than 30H), but will never look small.
Is H cup bigger than DDD?
Some US brands use a D-E-F sizing system, while others use a D-DD-DDD one. This means that a DDD equals a US F. Therefore, yes, H cup breasts are (two sizes) bigger than DDD ones.
How much do H cup boobs weigh?
H cup breasts all ‘project’ 8”. However, the larger the band size (and hence body), the wider the breasts and the more they weigh. According to the same article linked above:
- 28H breasts weigh about 1.5lbs each
- 30H breasts weigh about 1.7lbs each
- 32H breasts weigh about 2lbs each
H cup vs. G – 28G breasts weigh approximately 1.2lbs each, hence by going up one cup size you are carrying around an additional 0.6lbs or so!
H cup vs. I – 28I breasts weigh roughly 1.7lbs each, so are around 0.4lbs heavier than a 28H bust.
H cup breast reduction surgery
In the US in 2018, over 43,000 female breast reductions were carried out, so it is not an uncommon procedure. However, it is an invasive surgery that carries some level of risk.
If your chest is causing you back or neck pain, the first step should be to check if a better bra can solve it. Good H cup bras (that fit well) will distribute the weight of your bust around your body, reducing strain on your shoulders.
H cup sister sizes
The H cup sister sizes are G/DDDD (when you go up one band size) and I (when you go down one band size).
For example, the sister sizes of 36H are 38G/DDDD and 34I.
Best bras for H cup size
As well as the support features already mentioned, you may want to look for bras with a side support panel – when there’s a lot of breast tissue, this helps to bring it forwards, away from the underarm.
Here are two H cup bras with side support panels:
- Morgan Banded Underwire Stretch Lace Bra by Elomi (available in US 32-42H)
- Sachi Strappy Underwire Plunge Bra Bra by Elomi (available in US 32-42H)
I Cup Breasts
What is an I cup?
A US I cup size is one where the overbust measurement is 9” larger than the underbust one.
Example I cup measurements
32” underbust + 41” overbust = 32I
39” underbust + 48” overbust = 40I
42” underbust + 51” overbust = 42I
How big is an I cup size?
I cup breasts will be larger on larger band sizes than on smaller ones. However, as they stick out roughly 9” from the body, they are definitely a cup size that looks big.
I cups vs. H cups – I cups are one size up from an H, so while bigger, but the difference is not dramatic.
I cups vs. E/DD cups – although both of these are full-bust sizes, I cups add an extra 4” to the overbust measurement compared to an E, so will appear significantly larger!
Here are examples of I cup breasts on different band sizes – a US 30I (left) and US 36I (right):
How much do I cup breasts weigh?
I cup boobs will weigh more or less depending on their size, since they are larger (wider) on a larger band size.
For example, according to the Hourglass Lingerie article:
- 28I breasts weigh about 1.7lbs each
- 30I breasts weigh about 2lbs each
I cup breast reduction surgery
I cup boobs weighing you down? As explained above, breast reductions are a fairly common surgical procedure, but it is worth investigating whether problems such as back pain can be solved through simply switching bras.
Well-made, supportive I cup bras aren’t particularly cheap, but they certainly cost less than a breast reduction!
I cup sister sizes
The I cup sister sizes are H (when you go up one band size) and J (when you go down one band size).
For example, the sister sizes of 34I are 32J and 36H.
Best bras for I cups
The best I cup bras have support features beyond what you’d find in a DD cup bra. For example, the cups may have thicker, sturdier underwires. Or they may have multiple vertical seams rather than just one, to reinforce support and add more lift.
Here are two great I cup bras:
- Awareness Full Figure Underwire Bra by Wacoal (available in US 34-40I)
- Goddess Keira Underwire Banded Bra (available in US 34-46I)
J Cup Breasts
What is a J cup?
In the US, a J cup size means that your overbust measurement is 10” larger than your underbust one.
Example J cup measurements
30” underbust + 40” overbust = 30J
33” underbust + 43” overbust = 34J
42” underbust + 52” overbust = 42J
Below is a comparison of J cup breasts on different band sizes – a US 30J (left) and US 36J (right):
US J cups vs. UK J cups
Although most brands don’t continue with ‘D’ sizing beyond a G/DDDD, some do, and a US J cup is also sometimes known as a DDDDDDD or ‘7D’ cup. That makes it six sizes beyond a D.
In contrast, a UK J cup comes after a UK HH cup (there is no ‘I’ in UK cup sizing), which is nine sizes beyond a D. UK and US D cups are the same, hence when you are comparing US vs. UK J cups, the UK J is much larger.
How much do J cup breasts weigh?
According to the Hourglass Lingerie article referenced above, 28J breasts weigh approximately 2lbs each. But 28 is a small, fairly uncommon band size, so most J cup boobs will weigh more! The larger the band size, the wider the breasts and the more breast tissue they will contain.
J cup breast reduction surgery
If you have J cup boobs that are causing you considerable back or neck pain, then you are likely a good candidate for breast reduction surgery.
However, pain from heavy breasts is often caused by poorly-fitting bras. The band should provide around 80% of the support, but many women wear a band size that’s too loose to do its job correctly.
So before you make an expensive and invasive decision, it pays to have a professional bra fitting and see if better-fitting, better-made J cup bras could quite literally take that weight off your shoulders.
J cup sister sizes
The J cup sister sizes are I (when you go up one band size) and K (when you go down one band size).
For example, the sister sizes of 36J are 38I and 34K.
Best bras for J cups
J cup breasts are heavy, so the best J cup bras are designed first and foremost with support in mind. But that’s not to say that you can’t find pretty ones!
Here are two J cup bras that are supportive and stylish:
- Goddess Keira Underwire Banded Bra (available in US 34-46J)
K Cup Breasts
What is a K cup size?
In the US sizing system, a K cup size indicates that the overbust measurement is 11” larger than the underbust measurement.
Example K cup measurements
28” underbust + 39” overbust = 28K
34” underbust + 45” overbust = 34K
47” underbust + 58” overbust = 48K
Here is a quick comparison of K cups on different band sizes – a US 30K (left) and US 36K (right):
How much do K cup breasts weigh?
Unfortunately, there is not much data available about how much K cup breasts weigh. However, we can look at K cups. vs J cups plus K cups. vs I cups to get a general idea.
Considering that 28I breasts weigh roughly 1.7lbs per breast and 28J breasts weigh roughly 2lbs per breast, we can assume that each 28K cup breast would weigh somewhere in the region of 2.3lbs.
Of course, 30K breasts will weigh more than 28K breasts, as they are wider. And 32K breasts would weigh more than 30K breasts, and so on.
K cup breast reduction surgery
As with J cups, K cup boobs are very heavy whatever band size they’re on, but especially heavy on the larger band sizes. It’s imperative to seek out K cup bras that prioritize support, and ensure that you are not wearing a band size too large/loose for your needs.
However, should you still have back pain from your K cup chest even in a well-fitting and high-quality bra, you may want to consult a plastic surgeon to discuss a breast reduction. It’s one of the most commonly-performed surgeries, and highly effective at relieving pain and posture problems caused by plus size breasts.
K cup sister sizes
The K cup sister sizes are J (when you go up one band size) and L (when you go down one band size).
For example, the sister sizes of 40K are 42J and 38L.
Best bras for K cup breasts
The general guidelines when shopping for bras for K cup boobs are the same as for I and J cups. That is to say, look for wide bands, wide straps, seamed cups, and preferably some kind of side support. If the popular ‘3 part cup’ shape isn’t giving you the lift you need, you can find 4- or even 5-part cups in these larger sizes.
Here are two great K cup bras to check out:
- Goddess Keira Underwire Banded Bra (available in US 34-46K)
Large Bra Sizes – Comparison
Below are all of the cup size images together for easy comparison. Are some of them smaller than you were expecting? A DD cup for example is often thought of as being the biggest bra size, yet breasts can get significantly bigger than that!
Whatever your cup size, we say embrace it! Pretty bras may be harder to find in larger cup sizes, but it’s not impossible.
And if you’re suffering from breast-related pain, a high-quality bra that offers tons of support can really help. No, a chic and supportive bra won’t come cheap, but the comfort and confidence it brings is totally worth it.
P.S. Unsure of your cup size? Use our bra size calculator!