In UK bra sizing, B is one cup size larger than A, and C is one cup size larger than B.
The cup sequence around these sizes is: AA → A → B → C → D.
Each step represents roughly a 1 inch increase in the difference between the band measurement and fullest bust measurement. Cup volume also changes with band size, so an A, B or C cup is not a fixed volume on its own.
On this page:
Compare any three UK bra sizes in the A, B and C cup range.
The table below shows how A, B and C cup sizes compare within the UK bra sizing sequence when the band size remains the same.
| Cup Size | Position in Sequence | Band-to-Bust Difference |
|---|---|---|
| A | Before B and C | 1 inch |
| B | Between A and C | 2 inches |
| C | After A and B | 3 inches |
These differences describe the relationship between band and bust measurements. Cup volume itself also changes as the band size changes.
The diagrams below compare 34A, 34B and 34C using the same 34 band size. Keeping the band size the same makes it easier to see how cup volume increases through the UK sequence from A to B to C.
These are simplified educational diagrams designed to show relative cup-volume progression when the band size remains the same.
When the band size remains the same, cup volume increases through the UK cup sequence. A 34B has more cup volume than a 34A, while a 34C has more cup volume than both.
You can explore these sizes in more detail in our Best Bras for 34A, Best Bras for 34B and Best Bras for 34C guides.
In the UK bra sizing system, A, B and C are consecutive cup sizes. B sits directly between A and C in the UK cup progression.
AA → A → B → C → D → DD
When the band size remains the same, each step represents roughly a 1 inch increase in the difference between the band measurement and the fullest bust measurement. This is why B is one cup size larger than A, while C is one cup size larger than B.
Further along the UK cup-size sequence, the progression reaches D and then moves to the double-letter size DD. Other double-letter cup sizes, including FF and GG, are also used later in the sequence. These create additional steps within the cup-size progression. For a more detailed explanation, see our Double Cup Bra Sizes Guide.
You can explore the complete UK cup progression in our UK Bra Cup Size Chart.
Remember that cup volume also changes with band size. If you are moving between band sizes while keeping a similar cup volume, see our Bra Sister Sizes Guide or use the Bra Sister Size Calculator to compare equivalent-volume sizes.
Cup size is not a fixed volume. For example, a 32B, 36B and 40B all have different cup volumes because cup volume increases as the band size increases.
The same cup letter represents different bust measurements at different band sizes. The examples below show how the fullest bust measurement changes across A, B and C cup sizes as the band size increases.
| Band Size | A Cup | B Cup | C Cup |
|---|---|---|---|
| 32 | 33" | 34" | 35" |
| 34 | 35" | 36" | 37" |
| 36 | 37" | 38" | 39" |
| 38 | 39" | 40" | 41" |
If you want to explore A, B and C cup sizes in more detail, or compare them with the neighbouring cup sizes in the UK sequence, use the individual guides below.
Cup letters do not represent a fixed volume on their own, because cup volume changes as the band size changes. You can explore B and C cups across different UK band sizes using the guides below.
Yes. In the UK bra sizing system, B comes directly after A. When the band size remains the same, B is one cup size larger than A.
Yes. C comes directly after B in the UK cup size sequence. When the band size remains the same, C is one cup size larger than B.
The next cup size after C in the UK bra sizing system is D. The sequence around these sizes is A → B → C → D.
If you are unsure which bra size to start with, measure your underband and fullest bust and enter your measurements into our Bra Size Calculator.
You can then check the fit of your bra using our Bra Fitting Advice, compare international sizing systems with the Bra Size Converter, or explore equivalent-volume sizes with the Bra Sister Size Calculator.
If you want to compare bra sizes visually, use our UK Bra Size Visual Comparison Tool to compare sizes across the full UK size range.
For additional background on how bra sizing systems developed, you may also find this bra size overview useful.
