AA cup bras are available from a smaller selection of retailers and brands than many more common cup sizes, and availability can vary considerably by band size. This guide explains where AA sits in the UK bra size sequence, how AA cup volume changes across band sizes, which confirmed retailers currently offer AA sizes, and how to check your starting size before buying.
To confirm your starting size, begin with our Bra Size Calculator, then use our Bra Fitting Advice to check the band and cups. If you are comparing UK sizing with another sizing system, use our Bra Size Converter.
For a visual explanation of how AA cup volume changes across different band sizes, see our How Big Are AA Cups? guide.
An AA cup is part of the UK bra sizing system and sits immediately before A in the cup-size sequence. However, the cup letter alone does not represent one fixed breast volume because bra size combines both the band size and the cup size.
The nearby UK cup progression is: AA → A → B → C → D.
This means a 30AA, 34AA and 36AA all have different overall cup volumes even though they use the same AA cup letters. As the band size increases, the overall cup volume also increases.
A UK AA cup sits immediately before A in the UK bra cup-size sequence. However, an AA cup does not represent one fixed breast volume because the overall size depends on both the band size and the cup size.
For example, a 30AA has less overall cup volume than a 36AA, even though both use the same AA cup letters. Body proportions, breast shape and bra construction can also affect how a particular AA size appears in practice.
For a more detailed visual explanation, see our How Big Are AA Cups? guide.
An AA cup sits immediately before A in the UK bra size sequence. The simplified diagrams below show how cup volume increases gradually when the band size stays the same.
AA comes before A, and cup volume increases step by step across the sequence.
34AA
34A
34B
These are simplified educational diagrams designed to show how cup volume changes across nearby UK cup sizes when the band size remains the same.
When the band size stays the same, cup volume increases through the UK cup sequence. A 34A has more cup volume than a 34AA, while a 34B has more cup volume than both.
For a more detailed visual explanation, see our How Big Are AA Cups? guide.
How cup sizes work: A bra size combines both a band size and a cup size. In the UK cup-size sequence, AA sits immediately before A, followed by B, C, D and the larger cup sizes.
The cup letter does not represent one fixed breast volume. For example, a 34AA has more overall cup volume than a 30AA because cup volume increases as the band size increases. This is why both parts of the bra size need to be considered together.
AA cup bras are available from a smaller selection of brands and retailers than many more common cup sizes. Current confirmed options include Marks & Spencer, the Naturana Cotton Wireless Bra and specialist retailer Ample Bosom.
Product, style and colour availability can change, so always check the retailer's current listings before ordering.
The Naturana Cotton Wireless Bra is available in selected AA sizes from 34AA to 44AA.
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Based on the AA availability confirmed for this guide, the following band-and-cup sizes are currently represented across these retailers and products:
Together, these confirmed options cover AA sizes from 28AA through 48AA, although not every retailer carries every band size within that range.
UK and US bra sizing use similar band numbers, but cup lettering can vary as sizes increase. For AA cups specifically, AA is used in both UK and US sizing, so the same cup letters may appear in both systems.
When comparing international sizes, check the full bra size rather than the cup letter alone. You can use our Bra Size Converter to compare UK sizing with other systems, or see our UK vs US Bra Size Comparison Guide for more detail.
In many cases, the AA cup lettering is the same in UK and US sizing. However, the full bra size still needs to be checked because sizing systems and manufacturer size charts can differ.
Before ordering, confirm whether the retailer is using UK, US or another sizing system and compare the complete band-and-cup size using the Bra Size Converter.
Many people assume that all AA cups are the same size. In reality, cup volume increases as the band size increases. A 38AA holds more overall cup volume than a 34AA, while a 30AA holds less.
The cup letter stays the same, but the overall cup volume increases as the band size increases.
30AA
34AA
38AA
These simplified educational diagrams show how cup volume changes as the band size increases, even when the cup letter remains AA.
A bra size combines both the band size and the cup size. This is why a 38AA holds more cup volume than a 34AA, while a 30AA holds less, even though all three use the same AA cup letter.
This is also why cup letters should never be judged on their own. If you want to understand how cup volume relates across nearby sizes, see our Bra Sister Sizes Explained guide.
Measure your underband and bust, then enter your details into our Bra Size Calculator to get a recommended UK starting size.
For step-by-step measuring guidance and fit checks, use our Bra Fitting Advice.
If the fit is not right, review the band and cup fit separately and compare your measurements with our Bra Fitting Advice. You can also use our Bra Size Converter when comparing UK sizing with another sizing system.
Sister sizes use different band and cup combinations with a similar overall cup volume. When moving down a band size, the cup letter moves up to help maintain a similar cup volume.
This can be useful when an exact AA size is unavailable, although the band length will be different. Always check the complete fit rather than choosing a sister size based on cup volume alone.
A useful AA cup example is:
These sizes have a similar cup volume but use different band sizes.
30B
32A
34AA
These simplified diagrams illustrate how sister sizes can have broadly similar cup volume even though the band size and cup letter change.
Moving from 34AA to 32A to 30B reduces the band size while increasing the cup letter, helping to maintain a similar overall cup volume.
For a full explanation of equivalent-volume sizing, see our Bra Sister Sizes Guide.
You can also use our Bra Size Converter when comparing UK sizing with other sizing systems.
If you want to explore AA cup sizing in more detail, these related guides explain cup volume, sister sizing and how AA compares with nearby UK cup sizes.
Is AA a small bra size?
AA is one of the smaller cup sizes in the UK bra sizing sequence. However, overall breast volume depends on both the band size and cup size, so an AA cup on a larger band has more cup volume than an AA cup on a smaller band.
What is the difference between AA and A?
In UK bra sizing, AA sits immediately before A in the cup-size sequence. When the band size remains the same, an A cup has more cup volume than an AA cup.
What does AA mean in bra sizing?
AA is a UK cup size that sits immediately before A in the cup-size sequence. The cup letter is combined with a band size, so AA does not represent one fixed breast volume.
Is a UK AA cup the same as a US AA cup?
AA cup lettering is used in both UK and US sizing. However, always check the complete band-and-cup size and the sizing system used by the retailer or manufacturer when comparing sizes.
Does band size affect AA cup volume?
Yes. Cup volume increases as band size increases. For example, a 38AA has more overall cup volume than a 32AA even though both use the same AA cup letters.
What cup size comes after AA?
In the UK bra size sequence, A comes immediately after AA. The nearby progression is AA → A → B → C → D.
For additional background on bra sizing systems and cup-size terminology, see the bra size reference on Wikipedia .
If you are unsure which bra size to try, start by measuring your band and bust and entering the measurements into our Bra Size Calculator.
You can then review our Bra Fitting Advice to check how the band, cups and straps should sit, and use the Bra Size Converter when comparing UK sizing with other sizing systems.
