Bra size conversion chart
US, UK and EU band and cup conversions, plus sister sizes — with the variance stated rather than implied, because cup systems genuinely diverge above a D and no brand is bound to any of them.
The band number converts cleanly between markets; the cup letter does not. Use these tables to get to the right neighbourhood, then let the brand's own chart have the last word — it is the only one graded to their actual blocks.
Band sizes — US/UK, EU, FR/ES/BE, IT and AU
The band number is the stable half of a bra size: it tracks the underbust measurement, and the regional systems are arithmetic translations of each other. US and UK use the same inch-based numbers.
| US / UK | EU | FR / ES / BE | IT | AU |
|---|---|---|---|---|
| 28 | 60 | 75 | 0 | 6 |
| 30 | 65 | 80 | 1 | 8 |
| 32 | 70 | 85 | 2 | 10 |
| 34 | 75 | 90 | 3 | 12 |
| 36 | 80 | 95 | 4 | 14 |
| 38 | 85 | 100 | 5 | 16 |
| 40 | 90 | 105 | 6 | 18 |
| 42 | 95 | 110 | 7 | 20 |
| 44 | 100 | 115 | 8 | 22 |
The arithmetic: EU = centimetre underbust rounded to the nearest 5, French and Spanish sizes run EU + 15, and Australian bands follow dress sizing. Band conversion is the trustworthy row of this page — if a converted size fails, suspect the cup first.
Cup sizes — where US, UK and EU diverge
Cups A through D mean roughly the same thing everywhere, and everything above a D diverges by market. This is the single most error-prone conversion in apparel: read each column as that market's ladder, one rung per row.
| Bust − band | US | UK | EU |
|---|---|---|---|
| 1 in / ~2.5 cm | A | A | A |
| 2 in / ~5 cm | B | B | B |
| 3 in / ~7.5 cm | C | C | C |
| 4 in / ~10 cm | D | D | D |
| 5 in / ~12.5 cm | DD or E | DD | E |
| 6 in / ~15 cm | DDD or F | E | F |
| 7 in / ~17.5 cm | G | F | G |
| 8 in / ~20 cm | H | FF | H |
| 9 in / ~22.5 cm | I | G | I |
| 10 in / ~25 cm | J | GG | J |
Above a D the systems genuinely disagree: a US DDD, a UK E and an EU F describe roughly the same cup, and the UK ladder inserts double letters (DD, FF, GG) where the US and EU mostly do not. Brands also deviate from their own market's convention, so past a D treat any converted size as a starting point for that brand's chart, not a destination.
Sister sizes — same cup volume, different band
Each row holds the cup volume constant: go up a band and down a cup letter (or the reverse) and the cup itself holds roughly the same amount. This is the one table here that is arithmetic rather than convention, and it is the standard fix when a bra fits in the cup but not the band.
| Down one band | Your size | Up one band |
|---|---|---|
| 28D | 30C | 32B |
| 30D | 32C | 34B |
| 32D | 34C | 36B |
| 34D | 36C | 38B |
| 30E/DD | 32D | 34C |
| 32E/DD | 34D | 36C |
| 34E/DD | 36D | 38C |
Sister sizing changes the band, and the band changes how the same cup sits — it is a fallback, not an equivalence. Use it when a brand's run stops before your size, or when the cup fits and the band does not.
Measure instead, where you can
Every table above translates labelling conventions. The two measurements underneath them are the actual quantities, and they convert perfectly because they are just lengths:
- Band: snug around the underbust. Round to the nearest even number in inches for US/UK sizing, or to the nearest 5 cm for EU. If you round up for comfort, expect to sister-size the cup up with it.
- Cup: fullest part of the bust, minus the band. Each inch of difference is one cup step on the US ladder. Past four inches, convert the difference — not the letter — between markets.
- When two sizes both seem right, fit the band first. The band does most of the structural work; the cup can be sister-sized around it.
If you are the one selling
For intimates listings the highest-leverage fixes are the least glamorous: publish the band and cup measurements your grading actually uses rather than only the size label, state which market's ladder your cups follow, and put the model's size on every on-model image so shoppers can calibrate the photo against themselves. For the general apparel version of this page, see the clothing size conversion charts.
What no chart shows is how a style sits on different bodies — that is an imagery problem, and it is the one we work on: on-model photos across body types from the product shots you already have, on the AI lingerie models page, with the background reading in the AI lingerie photography guide.
Common questions
Is a US DD the same as a UK DD?
At DD itself, effectively yes. One step further up they split: the next US cup is DDD (often written F), while the next UK cup is E — and an EU F sits at roughly the US DDD / UK E level. Above a D, always convert through the bust-minus-band measurement rather than the letter.
What is a sister size?
The same cup volume on a different band: go up a band, down a cup letter — or down a band, up a letter. 34C, 32D and 36B hold roughly the same cup. It is the standard adjustment when the cup fits and the band does not, or when a brand's size run stops one step short of yours.
Why does my cup size change between brands?
Because a cup letter is relative to the band, and both are graded to each brand's own block, not to a standard. There is no enforced standard for bra sizing in any major market — the letter is that brand's shorthand, which is why the measuring method below beats any conversion.
How do I measure without a fitting?
Two numbers with a soft tape: snug around the underbust for the band (round to the nearest even number in inches, or nearest 5 cm for EU), and around the fullest part of the bust, unpadded, for the cup. Each inch of difference between the two is one cup step — 1 inch A, 2 inches B, and so on, on the US ladder. Methods differ slightly by brand, which is one more reason their chart outranks this one.
Do these tables cover sports and swim tops?
Only loosely. Sports tops are frequently sold in alpha sizes (S/M/L) that flatten band and cup into one letter, and swim tops often follow dress sizing instead. Where a listing offers band-and-cup sizing, the tables above apply; where it offers alpha sizing, you are back to that brand's own chart.
These are typical conversions compiled from common regional convention, not a standard — no major market enforces one for bra sizing, and no table here is authoritative for any individual brand. Always check the brand's own chart, and treat measurements as better evidence than labels. Last reviewed September 2026. Spotted an error? Tell us and we'll correct it.
Show the fit, not just the numbers
A chart answers what a size means. On-model imagery answers how the style sits — from one product photo, across the body types you actually sell to.