UK bra sizes combine two numbers: a band size (your underbust measurement, rounded to the nearest even inch) and a cup letter (the difference between your bust and band). Sizes run from 28AA up to 44G and beyond, with sister sizes covering the gaps in between — so almost every measurement has a match.
How UK Bra Sizing Works
Your band comes from your underbust measurement, taken snugly without a padded bra and rounded to the nearest even number. Your cup comes from the difference between your bust and band measurements — every extra inch of difference moves you up one cup letter. This is the direct-measurement method used by most UK fitters today, rather than the older method of adding several inches to the underbust reading.
UK cup sizes run in a fixed order: AA, A, B, C, D, DD, E, F, FF, G and beyond. Each step up the ladder represents roughly a one-inch difference between bust and band, so the progression is easy to predict once you know your band.
UK Bra Size Chart
Here's the quick-reference version. For the full breakdown with underbust ranges in inches and centimetres, see our complete UK bra size chart.
| UK Size | Underbust | Cup Letter | Bust–Band Difference |
|---|---|---|---|
| 28AA | 28" | AA | 0" |
| 30A | 30" | A | 1" |
| 32B | 32" | B | 2" |
| 34C | 34" | C | 3" |
| 36D | 36" | D | 4" |
| 38DD | 38" | DD | 5" |
| 40E | 40" | E | 6" |
| 42F | 42" | F | 7" |
| 44G | 44" | G | 8" |
UK Bra Sizes in Order: Smallest to Biggest
Listed smallest to largest, UK bra sizes in order run roughly: 28AA, 30A, 32B, 34C, 36D, 38DD, 40E, 42F, 44G — with sister sizes filling every gap in between.
What Is the Smallest UK Bra Size?
The smallest bra size UK retailers commonly stock is 28AA — a 28-inch band with almost no difference between bust and band measurement. Specialist fitters and some online-only brands go smaller still, down to a 26 band, for anyone whose underbust falls below the standard 28-inch starting point.
What's the Biggest UK Bra Size?
Mainstream UK shops usually top out around 44G or 46GG. Specialist fitters and made-to-measure brands go considerably further, supplying bands past 50 and cups into the K–N range for anyone mainstream stock doesn't cover.
How Many UK Bra Sizes Are There?
Between the smallest and largest band, there are well over 100 combinations once you count every band-and-cup pairing — far more than the handful most mainstream stores keep on the shelf at once. The logic stays the same throughout, whether you're a 28 band or a 44 band: measure, find the difference, match to a letter.
Converting to US, EU and Other Sizes
Buying from a non-UK brand? The underlying maths is simple: US cups match UK cups letter-for-letter up to D, then run one letter ahead (UK DD = US E, UK E = US F). See our full UK vs US vs EU conversion guide for band size conversions too.
Not sure which UK size you're starting from? Use our bra size calculator to get your band, cup and sister sizes in one go, or read our guide on how to measure your bra size at home for the full step-by-step walkthrough.
Frequently Asked Questions
Is UK sizing the same as US sizing?
No. Band numbers match, but cup letters diverge from D upward — a UK DD equals a US E, and a UK E equals a US F. Below D, most brands label cups the same way in both systems, so mismatches usually start once you're a D cup or larger.
Why do two different brands give me different results?
Every brand cuts to its own block, so a size that fits perfectly in one label can run tight or loose in another. Treat your calculated result as a reliable starting point, then adjust by one band or cup size either way when trying a new brand.
How often should I re-measure?
Roughly every 6–12 months, or sooner after any weight change, pregnancy, or long break from wearing a properly fitted bra. Bands and cups both shift more than people expect, even from a few kilograms of change.
Do I need to remove my bra before measuring?
Yes — measure over bare skin or a thin, unpadded bralette. Padding and underwire both distort the bust reading and will throw off your cup result.
What if my two measurements don't match a standard size exactly?
Round the band to the nearest even number and the cup to the nearest whole inch of difference. If you land between two results, a sister size — same volume, different band-cup combination — is usually the better fit.
Ready to find your perfect bra size? Try our free UK calculator.
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