UK to US Bra Cup Size Conversion
| UK Cup | US Cup |
|---|---|
Sizing conventions vary by brand and by cut — this table shows the standard published conversion. Always check the garment's own size chart when one is available. See how these tables are compiled.
A cup letter means little without its band
Converting a UK cup letter to US sizing without specifying the band size is an incomplete question, since cup size describes a volume relative to underbust measurement rather than an absolute quantity — a UK F on a 32 band and a UK F on a 38 band represent very different actual bust volumes, so any honest conversion needs the band size alongside the cup letter.
From A through D, UK and US cup letters align directly, making this the more straightforward part of the range. Above D is where the systems diverge: UK sizing continues into DD, E, F, FF, G, GG, H and beyond, while mainstream US sizing has historically stopped expanding as far, often reusing 'DD' or 'DDD' rather than introducing new letters for the equivalent range.
Sister sizing explains why there isn't one fixed answer
Because cup volume is the bust-minus-band difference rather than a standalone figure, the same volume can be represented by a smaller band with a bigger cup letter, or a larger band with a smaller cup letter — shifting one band size while moving the cup letter one step in the opposite direction keeps the represented volume roughly equivalent, which is the actual mechanism behind converting a cup letter across systems.
US specialty retailers close the resolution gap above D
Where mainstream US department-store brands have historically offered less cup-letter granularity above D than UK sizing does, US specialty and fuller-bust-focused retailers have increasingly adopted extended lettering (DD, DDD, and further) specifically to serve customers whose UK size doesn't map cleanly onto standard US options.
Pairing band and cup before you convert
Always pair your UK cup letter with its band size before converting, use the sister-sizing relationship to explore adjacent combinations if the first conversion doesn't fit, and check a US specialty retailer's chart specifically for anything past a D cup, since mainstream US lettering may not offer a precise equivalent.
Different bra styles handle the same cup letter differently
A balconette style and a full-coverage style in the identical converted cup letter and band size distribute the same volume across different amounts of coverage, so the letter conversion getting the volume right doesn't guarantee a comparable look or coverage level — check the specific style's own fit notes in addition to the converted size, especially when trying an unfamiliar US brand's balconette, plunge, or full-cup styles for the first time.
Frequently asked questions
Can I convert my UK cup letter to US sizing without my band size?
Not meaningfully — cup volume is relative to the band measurement, so the identical cup letter represents a different actual volume on different band sizes. Convert cup and band together.
Why doesn't my UK F cup have one obvious US letter equivalent?
Mainstream US bra sizing has historically offered less lettered resolution above D, often reusing 'DD' or 'DDD', while UK sizing continues with distinct letters (E, F, FF, G, and further) for what the US market compresses into fewer labels.
What is sister sizing and how does it help here?
Moving one band size while adjusting the cup letter one step in the opposite direction keeps the represented cup volume roughly constant — it's the actual mechanism that makes cup-letter conversion meaningful across systems.
Are US specialty retailers more useful than mainstream brands for this conversion?
Often yes, particularly above a D cup — specialty and fuller-bust-focused US retailers have adopted extended lettering closer to the UK convention than typical mainstream department-store brands offer.
Is the UK-to-US conversion reliable for A through D cups?
Yes, that range converts directly and reliably — the real complexity is concentrated above D, where the two systems' cup-lettering conventions genuinely diverge.
Does the cup-letter conversion account for different bra styles like balconette or full-coverage?
Not directly — the letter conversion addresses volume, but different styles distribute that volume across different amounts of coverage, so check the specific style's own fit notes alongside the converted size.