Understanding the difference between D and DD cups can be confusing, because the two sizes sound so alike. The short answer is that a DD cup is one cup size bigger than a D cup on the same band. A D cup means your bust measures about 4 inches more than your ribcage, and a DD cup about 5 inches more. That one inch makes a noticeable difference in how a bra fits, and it is why so many people wearing a D are better supported in a DD. Wearing the wrong bra size is common, and a D that should be a DD is one of the most frequent mix-ups. This guide explains the difference, how DD compares with an E cup and with US sizes like DDD, and how to tell which bra cup size fits you.
The short answer
D vs DD at a glance
Everything below in three lines.
- DD is bigger than D. On the same band, a DD cup is one size up from a D, roughly one extra inch of bust.
- DD and "double D" are the same. In UK sizing DD comes straight after D, then E, F and FF.
- The band changes everything. A 30DD holds less than a 38D, so a cup letter only means something next to its band.
The Difference Between D And DD Cups
Cup sizes are worked out from the difference between your bust measurement and your band measurement. Each inch of difference is one cup up the ladder, so your bust size relative to your band size decides your cup letter. A D cup sits at a 4 inch difference and a DD cup at a 5 inch difference, so on the same band the DD cup is deeper and holds more. Measure your band around the rib cage just under your bust, then measure around the fullest part of your bust, and the gap between the two gives you your cup.
D
About 4 inches
Bust measures around 4 inches more than the ribcage.
DD
About 5 inches
Bust measures around 5 inches more than the ribcage. One cup bigger than D.
Getting The Right Fit
Ever noticed how the fit of your bra band and underwire changes as you move between sizes? Though cups are typically cut wider, and some deeper, as the size increases, there is a remarkable difference in both cup shape and band width between brands. It's essential therefore to remember that not every D cup will fit the same, and not every DD cup will fit the same on your body.
Cup vs Band Sizes
Another critical bit about cup sizes is that they need two parts. They need both the cup size and the band size to make sense. That "DD cup" doesn't exist on its own. The band size must be paired with it for comparison purposes, meaning a 30DD is both smaller than a 38DD in terms of the circumference measurement and also when looking at its capacity as well.
Band sizes can span from a petite 26 inches to an expansive 46 inches, while cup sizes range anywhere from the diminutive AA cup up to and beyond the generous J cup.
Bra size is calculated by taking both your chest circumference (measured around the rib cage just below your bust) and your breast volume into account. Generally, each inch increase in chest measurement equals a one-cup size increase.
Unsure of the right bra size for you? Take a look at our fitting guide which provides step-by-step instructions to help identify what defines a well-fitting bra and how to adjust it accordingly.
What Is The Difference Between DD+ Sizes And A-D Sizes?
If the fullest part of your bust measures 5 inches or more than the circumference of your ribcage, a DD+ bra is likely to fit and offer you optimum comfort. With firmer underwires and extra pattern pieces in each cup for additional support, these bras are specifically made with sturdier fabrics and components that can accommodate fuller busts. Browse our D+ bras to see the range.
Why The Difference Between D And DD Bras Matters
Recently, DD+ sizes have become much more prevalent. Various companies that manufacture bras in small cup sizes (A-D) now produce them for DD size and beyond too.
Remember that the band and cup work together. Every time your band size goes up, your cup letter goes down to hold the same volume, and every time your band goes down, your cup letter goes up. These matching sizes are called sister sizes, as the table below shows.
Sister sizes: each row holds the same cup volume
| 28 |
30 |
32 |
34 |
36 |
38 |
40 |
| 28E |
30DD |
32D |
34C |
36B |
38A |
40AA |
| 28F |
30E |
32DD |
34D |
36C |
38B |
40A |
| 28FF |
30F |
32E |
34DD |
36D |
38C |
40B |
| 28G |
30FF |
32F |
34E |
36DD |
38D |
40C |
| 28GG |
30G |
32FF |
34F |
36E |
38DD |
40D |
| 28H |
30GG |
32G |
34FF |
36F |
38E |
40DD |
So a 34DD holds the same cup volume as a 36D and a 32E. Our guide to bra sizes explained covers sister sizes in more detail.
Is DD The Same As E? And What Is DDD?
In UK sizing, no. DD and E are two different cup sizes, and E is one cup bigger than DD. The UK ladder runs D, DD, E, F, FF, G and so on, with no DDD at all.
The confusion comes from US sizing, which labels cups differently above a D. In the US, DD and E are often used for the same cup, and DDD, sometimes called triple D, is roughly equivalent to a UK E. Conversions vary from brand to brand, so if you see a DDD you are almost certainly looking at a US size.
UK and US cup sizes compared
| UK |
US |
| D |
D |
| DD |
DD / E |
| E |
DDD / F |
| F |
G |
| FF |
H |
Approximate, as each brand's sizing system varies. All lingerie at Uplifted Lingerie uses UK sizing, so you can use the UK column of any size chart with confidence.
A DD is one cup bigger than a D. A DDD is not a UK size at all. It is a US label for roughly a UK E.
Sizing Guide For D And DD Cups
Who Should Wear A D Cup?
If you usually wear a C cup and your chest area is now overflowing out of the bra cups, you may want to look into sizing up. A D cup will fit more snugly than its DD counterpart.
Who Should Wear A DD Cup?
If your breasts are larger than a D cup size and spilling out of the top or sides, you should consider opting for a DD cup instead. Similarly, if you're wearing an E cup and find that the cup doesn't sit smoothly against your breasts, then you might want to try a DD instead.
When To Size Down To A D Cup
If you normally wear a DD bra but it now feels too big in the cups, you may need to switch down to a D cup if your band fits well but the cups feel too big. The cup of an appropriately sized bra should encase all breast tissue without gaps in its shape. As 85 to 90% of the support from your bra comes from the band, this area needs to stay secure even when straps are taken off the shoulders.
When To Size Up To A DD Cup
Do you experience any discomfort or breast tissue spillage in your D cups? If so, we strongly advise that you size up to a DD cup. Always focus on how the bra actually fits instead of looking at its tag. Your size is just a suggestion rather than a fixed law, so let yourself explore outside of your comfort zone and discover something new.
Is A 34DD Or 36DD Big?
Not especially. A 34DD holds the same cup volume as a 36D or a 32E, and many brands treat DD as the start of their fuller-bust range rather than the top of it. Whether a size looks big depends on the band, which is why a 36DD holds noticeably more than a 30DD even though both are DD.
D And DD Bras We Recommend
Fantasie Belle
A supportive underwired full cup bra with a lace upper, a dependable everyday choice in D, DD and beyond.
View Fantasie Belle →
Fantasie Illusion
A side support bra that lifts and centres, useful if a D cup spills at the sides and you are moving up to DD.
View Fantasie Illusion →
Panache Tango
An underwired balconette with a rounded, uplifted shape, a popular choice across D and DD cups.
View Panache Tango →
Shop all D+ bras →
FAQs
Is D or DD cup bigger?
A DD cup is bigger. The cup sizes A, B, C and D are the core ones, and as you move up the UK ladder DD is one size larger than D. The pattern continues through E, F and FF, so E is bigger than DD just as DD is bigger than D. This only holds on the same band, since a 30DD holds less than a 38D.
How much bigger is DD than D?
On the same band, a DD cup is one cup size bigger than a D, which works out at roughly one extra inch of bust measurement. A 34D fits a bust about 4 inches bigger than the ribcage, and a 34DD about 5 inches bigger.
Is a 36D the same as a 34DD?
They hold the same cup volume, because they are sister sizes. The 36D has a looser band and the 34DD a firmer one. If a 36D fits the cups but the band rides up, a 34DD is usually the better fit.
Is 32DD the same as 34D?
Yes, in cup volume. A 32DD and a 34D are sister sizes, so the cups hold the same amount and only the band differs. Choose the one whose band sits firm and level around your ribcage.
Double D? Is that different to DD?
No, double D and DD are the same size. Saying "double D" is simply saying two of the same letter instead of repeating them. In the same way, double F means FF and double G means GG.
What does DD mean in bra size?
DD is the cup size that comes after D. It means your bust measures about 5 inches more than your ribcage. It is always paired with a band number, for example 34DD, which tells you both the band and the cup.
Is DD the same as E?
Not in UK sizing. In the UK, E is one cup bigger than DD. In US sizing, DD and E are often used for the same cup, which is where the confusion comes from. Check whether a bra uses UK or US sizes before you buy.
What is a DDD cup in UK sizes?
There is no DDD in UK sizing. DDD, or triple D, is a US size, and it is roughly equivalent to a UK E cup. The exact conversion varies by brand, so it is worth measuring and using UK sizes where you can.
Is the DD cup size big? Or small?
While a 38DD has more cup volume than a 30DD, DD is merely the beginning of the range for many brands. The idea of DD as a very large size has lasted because larger sizes were hard to find for a long time. These days wearing a DD cup is common, and with cup sizes going as high as L and beyond, DD is by no means the biggest option available.
Why is bra fitting so important?
Bra size gives you a starting point, but each brand fits a little differently, even in the same size. Observing how a bra fits on the body is the best way to get a supportive fit. Bands should sit flat against the body and not ride up, straps should not dig in, and cups should be filled but not overflowing.