The biggest commercially available bra cup size is a UK L cup, which is equal to a US Q cup. However, some women require even larger cup sizes that go beyond the typical sizing charts.
What bra cup sizes are available?
Most standard bra size charts include cup sizes from AA to DDD or E in the US and double letters AA to FF in the UK. Here is an overview of the common cup size ranges:
- AA cup: The smallest cup size available, for women with very petite busts
- A cup: For women with smaller busts
- B cup: Considered an average or medium bust size
- C cup: For fuller busts that are larger than average
- D cup: A large cup size, indicating a full bust
- DD or E cup: An extra large cup size, for very full busts
- DDD, F, or FF cup: The largest commonly available cup sizes at most lingerie stores
However, some specialty bra companies offer larger cup sizes beyond the typical DDD/F cups, using double and triple letters such as G, H, J, K, and L in the UK system. In the US, these larger cups are usually designated with triple and quadruple D’s and E’s like DDD, H, K, N, Q etc.
What is the L cup size?
In the UK sizing system, an L cup is two sizes larger than an F cup and four cup sizes larger than a D cup. Each cup progression after a D represents adding an inch to the bust measurement. So here is how an L cup compares:
- D cup = 4 inch difference between bust and underbust
- DD or E cup = 5 inch difference
- F cup = 6 inch difference
- FF cup = 7 inch difference
- L cup = 8 inch difference
As a rough guide, a UK L cup would be suited for women with a 10 inch difference or more between their underbust and bust measurements. For example, someone with:
- 30 inch underbust
- 40 inch bust
This 10 inch difference indicates an L cup according to UK sizing charts. An L cup is designed to accommodate a very full, large bust.
Equivalent cup sizes
Since sizing systems vary by country, here are the cup sizes equivalent to a UK L cup:
| UK | L cup |
| US | Q cup |
| European | I cup |
| French | U cup |
So in both US and international sizing charts, an L cup (or its equivalent) represents one of the largest possible cup sizes.
Larger cup options
Some specialty bra makers offer cup sizes even larger than an L cup to meet the needs of women with exceptionally large busts. These ultra-large cup sizes include:
- M cup
- N cup
- O cup
- P cup
However, these extended cup sizes beyond L are not standardized across all brands, so a P cup from one company may not match an P cup from another company.
Bra fitting for larger cup sizes
Women who require an L cup or larger face challenges when bra shopping. Most mainstream lingerie stores do not stock cup sizes above an F. As a result, women with big busts often struggle to find bras that fit properly and provide enough coverage, support and comfort.
Here are some tips for larger busted women to find well-fitting bras in hard-to-find large cup sizes:
- Get professionally fitted at a lingerie store specializing in full bust brands and large cup sizes.
- Try both UK and US sizing when shopping online, since brands use different sizing scales.
- Look for full-figure brands like Goddess, Elila, Anita, Prima Donna, Elomi and Empreinte that cater to curvier shapes.
- Search for “full bust” or “full figure” styles with wide straps and sturdy band support.
- Choose bras with strong underwires and deep cups to lift and contain large breasts.
- Opt for full coverage cup styles to prevent spillage like balconette, full cup or plunge bras.
- Sister size up or down a band if needed to find your ideal cup volume (for example, try 32L, 34K, 36J etc).
With some effort to find the right brands and styles, women with L cups and bigger can get amazing support and flattering uplift.
Surgical options
In very rare cases, a woman’s breasts may grow so excessively large that they cannot find bras to fit, even with an L cup or larger. Oversized breasts can cause severe back pain, posture issues, and skin irritation. Some women in this situation opt to surgically reduce their bust size through breast reduction surgery.
During breast reduction, a plastic surgeon removes excess breast tissue and skin to reduce the overall cup volume. The nipple is also repositioned higher on the breast. This procedure not only allows women with gigantomastia (excessive breast growth) to fit into more typical bra sizes, but also alleviates associated physical discomfort.
It’s worth noting breast reduction patients rarely go down more than a few cup sizes, since the goal is a proportional, comfortable bust – not an extremely small chest. But even going down 2-3 cup sizes can make a huge difference in finding bras that fit properly.
Measuring for cup size
To determine your accurate bra cup size:
- Measure underbust:
- Wearing a snug bra, measure around the ribcage just below bust.
- Round to the nearest whole inch.
- Measure overbust:
- Measure around the fullest part of the bust.
- Round to the nearest whole inch.
- Calculate cup size:
- Subtract underbust from overbust measurement.
- Each inch of difference represents a cup size.
For example:
- Underbust: 34 inches
- Overbust: 42 inches
- Difference: 8 inches
- Cup size = UK L cup
This method will give you your true cup size, which you can then convert to your country’s sizing system. Proper bra fit is vital for support and comfort, especially for full busted women.
Conclusion
The largest commercially available bra cup size is typically an L cup in UK sizing and a Q cup in US sizing. These ultra-large cups are intended for women with bust circumferences 10 inches or greater than their underbust. While some specialty brands design cups beyond an L/Q, these extended sizes are not standardized. Women with gigantomastia who cannot find bra sizes large enough may consider breast reduction surgery. But in general, an L cup marks the current upper limit of standard bra cup sizing, designed to meet the needs of women with exceptionally full busts.
