What’s the difference between D and DD?

When it comes to bra sizes, the difference between a D cup and a DD cup is one of the most common sources of confusion. Though the two sizes are close in size, there are some key distinctions between them that determine which size a woman should wear. In this comprehensive guide, we will explain the sizing scale, look at how cup sizes are determined, and outline the key differences between D and DD cups.

How Are Bra Sizes Determined?

Bra sizes are made up of two components – the band size and the cup size. The band size refers to the circumference of the ribcage directly under the breasts. This measurement is rounded to the nearest even number to give the band size. For example, a measurement of 30.5 inches would have a band size of 32.

The cup size is determined by taking another measurement – the circumference around the fullest part of the bust. This number is then compared to the band size to calculate the difference. Each inch of difference represents a cup size. So if the bust is 32 inches, and the band is 30 inches, that’s a 2 inch difference – making the cup size a B. Here’s a quick rundown of how the cup sizes progress:

Cup Size Difference from Band Size
AA Less than 1 inch
A 1 inch
B 2 inches
C 3 inches
D 4 inches
DD 5 inches

So a 30D would mean a band size of 30 inches, and a bust measurement that’s 4 inches larger. The cup sizes progress in the alphabet from there, although after DDD/E cups the sizing switches to E, F, FF, G etc rather than double letters.

Key Differences Between D and DD

Now that we understand how the sizing works, what exactly is the difference between a D cup and a DD cup?

Volume and Coverage

The key distinction between a D and a DD cup is volume. Since going up a cup size represents an increase of 1 inch between the band and bust, a DD cup will have more volume and coverage than a D cup in the same band size. For example, a 30D bra is made for someone with a 30 inch underbust and 34 inch overbust. A 30DD is made for a 30 inch underbust and 35 inch overbust. While only an inch of difference, that extra inch means more breast tissue is able to fit comfortably in the DD cup.

Fit and Support

The other key difference between D and DD cups comes down to fit and support. If your breasts have a volume of more than 1 inch over your band size, trying to fit them into a D cup will usually result in spilling over the top or sides of the cups. A DD cup will be able to fully encapsulate the breasts without spillage or gapping.

The band size also impacts support. A 30DD will offer more support than a 36DD, because the band is tighter to keep the breasts stabilized. So both cup volume and band size are important for finding the ideal fit.

Common Misconceptions

There are some common misconceptions about D and DD sizes:

  • That DD cups are huge – Not necessarily. On a small band size like 30DD, the cups will be smaller and closer in volume to a D.
  • That D cups are small – D cups can look small or large depending on the band size. A D on a 40 band will look much different from a 30D.
  • That DD cups are twice as big as D – As explained above, DD cups only have an extra inch of volume over the same band size in D.

The look and fit of a cup size is so dependent on the band size, as well as breast shape, that two women can wear the same cup letter but look very different. Proper bra fit has more to do with how the bra supports and conforms to the breasts versus the letter itself.

How to Choose Between D and DD Cups

If you’re trying to decide whether to opt for a D or DD cup, here are some tips:

Get a professional bra fitting

Rather than try to guess your size, book a bra fitting with an experienced fitter. Many lingerie stores and department stores offer professional fittings, where the fitter will measure under the bust and fullest part of the bust and determine your proper size. They may also assess breast shape and give recommendations. A professional assessment is the best way to find your optimal D or DD size.

Try different sizes around your measurement

Use your bra measurements as a starting point, but don’t be afraid to try a range around that size. For example, if your measurements put you at a 30D, try both 30D and 30DD bras in the same style to compare the fit. The size that offers the most lift, coverage and comfort without gapping, bulging or tightness is your winner.

Assess fit for each style

Keep in mind that bra sizing can vary between brands, and even between styles. You may find you’re a perfect 30D in a demi style, but need to size up to a 30DD in a full coverage style from the same brand. Try on a few options while cup shopping.

Enlist help assessing fit

It can be hard to diagnose fit issues on your own. When trying on bras, bring along a friend or fitter who can look at the fit from all angles. Have them check for things like spillage, gapping, and whether the underwire sits flat under the bust.

Focus on support, not size

Rather than getting hung up on being a D or DD, shift your focus to whether a bra offers the lift, shaping and coverage you need. In some brands, their D cup may fit more like a DD. Don’t let a letter determine whether a bra works for you or not.

Common Bra Fitting Issues in D and DD Cups

Here are some common bra fit issues that come up in D and DD sizes, and how to fix them:


Spillage out of the cups indicates that the bra is too small. Try going up a cup size or two, especially if spillage is occurring at the top of the cup. For spillage at the center front, a style with more coverage may be needed.


Gapping, where there is empty space between the breast and the cup, signals cups that are too big. Try going down a cup size. Gapping can also be from cups that are the wrong shape – a demi may fit better for top fullness versus a full coverage style.

Underwire sitting on breast tissue

If underwires are sitting on breast tissue rather than smoothly encapsulating the breasts, cup sizes that are too small are usually the culprit. But also assess if the cup shape or wire width is a mismatch for your breasts.

Band riding up

A too large band will ride up the back. Tightening the band can help, or opting for a cup size up and band size down. A band that is overly tight can cause similar issues.

Shoulder straps digging in

If straps are leaving indentations, tightening them can help redistribute the weight. But more often, cups that are too small cause straps to overstretch to compensate. Moving up in cup size will take pressure off the straps.

Factors That Impact D vs DD Fit

Some factors that can influence whether a D or DD cup fits best include:

Breast fullness

Those with very full on top breasts often size up in cups for ample coverage. Side fullness or a wide breast root also may necessitate a larger cup size like DD.

Breast shape

Having a shallow breast shape versus projected breasts can impact what size fits best. Those with wide set breasts also tend to fit better in larger cup sizes.

Breast firmness

Firmer, self-supporting breasts may find a D cup provides enough support, while softer breasts that are more pendulous may prefer the greater coverage and lift of a DD.

Cup and band construction

Factors like cup height, wire width, placement of straps etc. all vary between bra styles and brands. These construction elements can mean a DD in one style fits more like a D in another.

Common Bra Styles for D and DD Cups

Here are some bra styles that tend to work well for D and DD cup wearers:

Demi Cup

Demi cup bras with a lowered cup height work well for breasts with minimal upper fullness. The shorter cup shows more cleavage while providing full coverage and support.


Balconette bras offer medium coverage with wide-set straps, making them a great pick for those with a wide breast root or side fullness needing containment.

Full Cup

Full cup bras fully encase the breasts, making them an ideal choice for DD wearers needing control, shaping and minimized bounce. Great for under clothing.


Plunge bras create cleavage with their lowered center gore, while still providing lift. Perfect under low cut tops.


Push-up bras enhance cleavage and lift with padding or underwires. DD cups can prevent spillage from the boost.


Unlined, wire-free bralettes offer a comfy option for at home wear and underneath oversized clothing or dresses.

Sports Bra

High impact sports bras minimize uncomfortable bounce during activity. Look for wide straps and strong support in cup sizes for larger busts.

Caring for Your D and DD Cup Bras

Get the most longevity out of your D and DD bras by following these care tips:

  • Always wash bras in a lingerie bag on the delicate cycle
  • Air dry bras to preserve elastic and prevent shrinking
  • Avoid putting bras in the dryer, which can damage fabric
  • Hand wash when possible to prolong life
  • Store bras folded in a drawer, not hung
  • Rotate bras between wears to allow for elastic recovery
  • Have 2-3 properly fitted bras and replace them every 6-12 months


While D and DD cup sizes are similar in volume, there are some key differences that make each more suited to certain breast shapes and sizes. Factors like breast fullness, firmness, placement on the chest, and the construction of the bra all impact whether a D or DD is the better fit. That’s why proper professional fitting along with trying a range of sizes is so important for determining your perfect match.

Rather than fixating on cup letters, it’s best to focus on how the bra makes your breasts look and feel – lifted, supported, shaped and comfortably encased. With some trial and error to find styles that tick those boxes, both D and DD cups can deliver a tailored fit and feminine silhouette.

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