Bra Size Guides

B Cup Bras by Band Size (UK) – Find the Best Bras for Your Exact Band Size

This B cup bras by band size guide helps you find the individual guide for your exact band size, with links to detailed pages for each available UK B band size.

A B cup sits within the UK bra sizing system between A and C. However a 28B, 34B and 40B represent different cup volumes because cup size changes with band measurement.

If you want to understand the size itself before choosing a band, see our B Cup Bras Guide or explore real-world measurements in our How Big Are B Cups explanation.

If you are unsure of your starting size, begin with the Bra Size Calculator. You can then confirm your fit using our Bra Fitting Advice and compare sizing across brands using the Bra Size Converter.

What Is a B Bra Size?

A B bra size is part of the UK bra sizing system and sits between A and C in the cup progression.

In most UK size charts, a B cup corresponds to roughly a 2 inch difference between the band measurement and the fullest bust measurement. Each step in the UK cup sequence typically represents about a 1 inch increase in this difference.

Cup size is not a fixed volume on its own. A 30B, 34B and 40B all represent different cup volumes because cup volume increases as the band size increases.

For a clearer picture of measurements and volume, see our How Big Are B Cups guide.

You can also compare B with neighbouring cup sizes using our B vs C vs D Cup Size Comparison or explore the wider UK sequence in our UK Bra Cup Size Chart.

If you are comparing different band sizes while keeping a similar cup volume, use our Bra Sister Sizes Guide or Bra Sister Size Calculator.

You can also explore detailed B-size guides for 32B, 34B and 36B.

Visual B Cup Comparison by Band Size

Compare B cup sizes across different UK band measurements to see how cup volume changes as the band size increases.

Want to compare every UK bra size? Use our UK Bra Size Visual Comparison Tool to compare all 220 UK bra sizes.

Popular B Bra Sizes

The guides below cover several B cup sizes across different UK band measurements.

Browse our B cup bras by band size directory below to find the individual guide for your UK band-and-cup size.

B Cup Bras by Band Size

Why Band-Specific B Guides Matter

Cup volume increases as band size increases. This means a 40B has more cup volume than a 30B, even though both use the same B cup letter.

Because band size and cup size work together, looking at the exact band-and-cup combination gives a clearer picture than considering the cup letter alone.

For example, a 32B bra, 34B bra and 36B bra all use a B cup letter, but each represents a different band measurement and overall cup volume.

Our B cup bras by band size directory brings together the available UK B sizes from 28B to 56B, making it easier to move directly to the guide for your exact band-and-cup size.

B Cup Bra Size FAQs

What is a B bra size?

A B bra size is part of the UK bra sizing system and sits between A and C in the cup progression. In most UK size charts, a B cup corresponds to roughly a 2 inch difference between the band measurement and the fullest bust measurement. For more detail, see our How Big Are B Cups guide.

Is B bigger than A?

Yes. In the UK cup sequence, B comes directly after A. When the band size remains the same, B is one cup size larger than A.

What cup size comes after B?

The cup size after B in the UK bra sizing system is C. The sequence around these sizes is A → B → C → D.

Does the same B cup have the same volume on every band?

No. Cup volume changes with band size. For example, a 30B has less cup volume than a 38B even though both use the same B cup letter.

For additional background on bra sizing systems, you may also find this bra size overview helpful alongside the guides on this site.

Browse the band-size guides above to go directly to the individual page for your exact UK B bra size.