Bra Size Guides

AA Cup Bras – Brands That Make AA Cups & How to Find Your Size

Shopping for a UK AA cup can sometimes be more challenging than finding larger cup sizes, as not all lingerie brands offer AA cups across their full size range. This guide focuses specifically on AA cup bras, including which brands commonly offer AA cups, how UK cup sequences work, and how to confirm your correct size before buying.

To confirm your starting size, begin with our Bra Size Calculator, then use the brand information below to shop with confidence.

Who This Guide Is For

• Women who wear a UK AA cup
• Shoppers who find the same AA size fits differently across brands
• Those comparing AA with A cup sizes
• Anyone comparing UK and international sizing
• People who want clearer guidance before buying everyday AA cup bras

Why Not All AA Cup Bras Are the Same

Although AA cup is a recognised UK bra size, bras can still vary in fit across brands and styles. This is not because the basic sizing rule changes, but because a bra size is made from both the band size and the cup size.

In UK sizing, AA sits before A in the cup sequence: AA, A, B, C, D, DD, E, F, FF, G, GG, H, HH, J, JJ, K.

This means a 30AA, 34AA and 36AA do not all have the same cup volume. The cup letter stays the same, but the overall cup capacity increases as the band size increases.

How Big Is an AA Cup?

A UK AA cup bra is the smallest standard cup size used by many UK lingerie brands and sits one cup size below an A cup in the UK bra size sequence. However, how large an AA cup appears depends on factors such as band size, body proportions and bra design.

For example, a 30AA and a 36AA do not have the same cup volume. Cup volume increases as band size increases, which is why the cup letter alone does not tell the full story.

AA Cup Size Progression

An AA cup sits before A in the UK bra size sequence. The diagrams below show how cup volume increases gradually while the band size remains the same.

These simplified educational diagrams show how cup volume increases across nearby UK cup sizes when the band size stays the same.

How cup sizes actually work: Bra cup sizes are based on a simple fitting rule — each step in the cup sequence represents a 1 inch difference between the bust and band size. This rule applies across all UK brands, regardless of whether they use a traditional or extended cup letter sequence.

The difference between brands is usually the lettering used, not the size step itself. For example, many fuller-bust brands include additional double letters such as FF and GG, while AA remains a standard UK cup size used across many traditional cup sequences.

UK Brands That Make AA Cup Bras

AA cup bras are available from a smaller selection of UK lingerie brands than A, B or C cups. The brands below offer verified UK AA cup availability and provide a useful starting point when comparing styles, band sizes and sizing systems.

• M&S – Bands 28–46, cups AA–K View size guide

AA Cup Band Sizes by Brand

Based on confirmed brand availability tables, these are the UK band sizes currently available in AA cup sizes across selected lingerie brands. Availability may still vary by individual style and collection.

• M&S: 28AA, 30AA, 32AA, 34AA, 36AA, 38AA, 40AA, 42AA, 44AA, 46AA

UK vs US Bra Sizes

Bra sizing systems vary slightly between regions. Most UK lingerie brands follow the UK cup size sequence, where AA sits before A.

Some US brands use different cup lettering conventions, which can create confusion when comparing sizes internationally. To understand how the sizing systems relate, see our UK vs US bra size comparison guide .

Is a UK AA Cup the Same as a US AA Bra Size?

Often, yes. Many UK and US brands use the same AA cup lettering, meaning an AA cup is frequently labelled the same in both systems.

However, sizing conventions can vary between manufacturers and regions. For this reason, always check the brand’s stated sizing system rather than relying on the cup letter alone.

AA Cup Volume Changes With Band Size

Many people assume that all AA cups are the same size. In reality, cup volume increases as band size increases. A 38AA holds more volume than a 34AA, while a 30AA holds less.

These simplified educational diagrams show how cup volume changes as the band size increases, even when the cup letter remains AA.

Popular Underwired AA Bras (UK Sizing)

These popular underwired AA bras are available in UK sizing from well-known lingerie brands. Underwired bras are less common in AA cup sizes than larger cup sizes, but several brands still offer options across a range of band sizes. Before purchasing, we recommend confirming your size using our Bra Size Calculator and reviewing our Bra Fitting Advice guide.

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How to Find Your Correct AA Cup Size

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.

Common Fit Issues for AA Cup Bras

• Band riding up at the back
• Cups gaping at the top edge or neckline
• Spillage at the top edge or sides
• Wires sitting on breast tissue at the sides
• Straps digging in or slipping off

If your AA cup fit feels inconsistent, try another style within the same brand or compare brands using our Bra Size Converter.

Can I Sister Size Instead of Wearing an AA Cup?

Sister sizing can help if your exact size is unavailable in a specific style, but it should be used carefully. If you go up a band size, you usually need to go down a cup size to keep a similar cup volume, and if you go down a band size, you usually need to go up a cup size. However, sister sizes can change where wires sit and how the bra supports you, especially across different shapes.

AA Cup Sister Size Example

When sister sizing, the band size changes while the cup volume stays similar. A common example is:

Sister Size Comparison

These diagrams provide a simplified visual example of sister sizing. While the band size changes, the overall cup volume remains broadly similar.

Some specialist manufacturers have historically produced AAA cup bras, which sit one cup size below AA in the UK cup sequence.

For a full explanation of how sister sizing works, see our Bra Sister Sizes Guide .

Use our Bra Size Converter to compare UK brand sizing and sister sizes accurately.

Explore More AA Cup Guides

If you want to compare AA cup sizes in more detail, these related guides can help you understand volume, band size and nearby cup sizes.

• A Cup Bras – Brands That Make A Cups & How to Find Your Size
• Bra Sister Sizes Guide

AA Cup Bra FAQs

Is AA a small bra size?
AA is one of the smallest standard UK cup sizes. However, a bra size combines both a band size and a cup size, so overall breast volume depends on the complete bra size rather than the cup letter alone.

What is the difference between AA and A?
In UK bra sizing, A is one cup size larger than AA. The sequence progresses AA, A, B, C, D, DD and beyond.

What does AA mean in bra sizing?
AA is a standard UK cup size that sits before A in the cup size sequence. A bra size combines both a band size and a cup size, so an AA cup can represent different volumes depending on the band size it is paired with.

Is a UK AA cup the same as a US AA cup?
Often, yes. Many UK and US brands use the same AA cup lettering, meaning an AA cup is frequently labelled the same in both systems. However, sizing conventions can vary between manufacturers and regions.

Does band size affect AA cup volume?
Yes. Cup volume increases as band size increases. A 38AA holds more volume than a 32AA, even though the cup letter remains the same.

What cup size comes after AA?
In the UK bra size sequence, A comes after AA. The sequence continues AA, A, B, C, D, DD, E, F and beyond.