Why do cup sizes vary between UK bra brands?

All UK bra sizing follows the same 1-inch rule, but brands use different cup letter sequences. This means the same cup letter can represent different volumes depending on the brand.

Does band size affect cup volume?

Yes. Cup volume increases as band size increases, so a 38 cup holds more volume than the same cup letter on a smaller band.

Is UK bra sizing the same as US or EU sizing?

No. UK, US and EU sizing systems use different cup progressions. Always use a conversion chart when comparing sizes across regions.

Bra Size Guides

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

Finding supportive bras in a UK JJ cup can be extremely challenging. Many brands stop well before this cup size, and even among specialist fuller-bust brands, availability can be limited. This guide focuses specifically on JJ cup bras, explaining which brands make them, which band sizes are available, and how JJ sizing works across different UK cup sequences.

To confirm your starting size, begin with our Bra Size Calculator, then explore the specialist brands listed below.

Who This Guide Is For

Women who wear a UK JJ cup
Those sized out of high-street and mainstream brands
Fuller-bust and fuller-figure customers
Shoppers comparing extended UK cup sizing
Anyone repeatedly sister-sized due to limited availability

Why Not All JJ Cup Bras Are the Same

Although JJ cup is a recognised UK bra size, not all JJ cups represent the same labelled step across brands. This is because different UK cup letter sequences are used by different brands, even though the underlying sizing rule is identical.

Bra cup sizes are determined by the difference between the band size and the fullest bust measurement. Each increase of 1 inch in that difference equals one cup size in the UK sizing system.

The difference between brands is not how the size is calculated, but which letters are used to label each step. Traditional UK brands follow a shorter cup sequence: B, C, D, DD, E, F, G, H, J, K.

Fuller-bust specialist brands use an extended UK cup sequence that includes additional double letters: D, DD, E, F, FF, G, GG, H, HH, J, JJ, K, KK, L, LL.

Each step in the UK cup size sequence represents a 1 inch increase in the difference between the underband and the fullest bust measurement. This rule applies to all UK brands, regardless of whether they use a traditional or extended cup letter sequence.

The only difference between brands is how those 1-inch steps are labelled. Traditional-sequence brands move directly from J to K, while extended-sequence brands include an additional step labelled JJ between J and K. The measurements increase in exactly the same way — only the letters change.

This difference is not related to support, quality or construction. It is simply the result of using different cup letter progressions. Both systems are valid UK sizing methods, but they are not interchangeable by letter alone.

The JJ cup is part of the UK’s extended bra size sequence, which includes several double-letter cup sizes such as FF, GG, HH, JJ and KK. These represent additional steps in the progression rather than half sizes. For a full explanation of how double-letter cups fit into the UK sizing system, see our Double Cup Bra Size Guide .

UK vs US Bra Sizes

Bra sizing systems vary slightly between regions. Most specialist fuller-bust brands such as Panache, Freya, Fantasie and Elomi follow the UK cup size sequence, which includes double letters such as FF, GG and HH.

Some US brands use a slightly different lettering system, 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 JJ Cup the Same as a US JJ Bra Size?

It depends on the brand. Many UK-based fuller-bust brands such as Panache, Freya and Elomi use the same extended UK cup sequence internationally, meaning an JJ cup is labelled the same in both the UK and US.

However, some US lingerie brands follow a different cup progression. For this reason, always check the brand’s stated sizing system rather than relying on the cup letter alone.

Important:
A cup size is not one fixed volume. Cup volume increases as the band size increases, so a 32JJ, 38JJ and 44JJ are all very different in fit and capacity.

Always consider both band size and cup size together when comparing bras.

UK Brands That Make JJ Cup Bras

Bravissimo – Bands 28–40, cups D–L View size guide
Panache – Bands 28–40, cups D–K View size guide
Elomi – Bands 32–46, cups D–K View size guide
Sculptresse – Bands 34–46, cups D–K View size guide

JJ Cup Band Sizes by Brand

Bravissimo: 28JJ, 30JJ, 32JJ, 34JJ, 36JJ, 38JJ, 40JJ
Panache: 28JJ, 30JJ, 32JJ, 34JJ, 36JJ, 38JJ
Elomi: 32JJ, 34JJ, 36JJ, 38JJ, 40JJ, 42JJ, 44JJ
Sculptresse: 34JJ, 36JJ, 38JJ, 40JJ, 42JJ

JJ Cup Bra FAQs

Is JJ cup bigger than J?
Yes. In extended UK sizing, JJ is one full cup step larger than J and one step smaller than K.

Do all brands offer JJ cups?
No. JJ cups are only available from specialist fuller-bust brands that use an extended UK cup sequence. Most high-street brands do not produce JJ cups.

Does band size affect JJ cup volume?
Yes. A 38JJ holds significantly more volume than a 32JJ. Always consider both band size and cup size together when assessing fit.

Can I sister size at JJ cup?
Sister sizing is rarely ideal at this cup level. Changing band size can significantly alter support, wire placement, and cup depth. If you are frequently sister sizing, the brand or cup shape may not be suitable.