A cup bra size: what it means, and what fits
An A cup is one inch of difference between bust and band, on whatever band you wear. A 30A and a 40A share a letter and nothing else. The letter is the same in the UK, US, EU and Australia; only Japan labels it B.
UK A: 1 in, 2.5 cm of difference
| UK | US | EU | FR | AU | JP (approx.) |
|---|---|---|---|---|---|
| 28A | 28A | 60A | 75A | 6A | B60 |
| 30A | 30A | 65A | 80A | 8A | B65 |
| 32A | 32A | 70A | 85A | 10A | B70 |
| 34A | 34A | 75A | 90A | 12A | B75 |
| 36A | 36A | 80A | 95A | 14A | B80 |
| 38A | 38A | 85A | 100A | 16A | B85 |
"a cup bra" gets about 12,100 Google searches a month in the US, 1,600 in the UK and 720 in Australia; "a cup size" adds 3,600 in the US. Google Ads cluster figures, September 2026.
Sister sizes keep the A cup's volume
Go down one band and up one letter, or up one band and down one letter, and the cup volume stays the same. Shown for UK A on a 32 band.
| UK | US | Compared with 32A |
|---|---|---|
| 30B | 30B | Tighter band, 1 letter up |
| 32A | 32A | This size |
| 34AA | 34AA | Looser band, 1 letter down |
The full diagonal chart, with fit fixes for a band that rides up or digs in, is on the sister sizes page.
What the +4 method does to this cup
The traditional method adds 4 inches to an even underbust and takes the cup from what is left. For UK A (1 in) that changes the answer on every band.
| Underbust | Bust | Measured band | +4 method (US) |
|---|---|---|---|
| 28 in | 29 in | 28A | 32 (below AA) |
| 32 in | 33 in | 32A | 36 (below AA) |
| 36 in | 37 in | 36A | 40 (below AA) |
White and Scurr (2012) found the traditional method overestimated band size and underestimated cup size (Ergonomics 55(6)). A size from an older calculator may not be the size on this page.
Which charts list it
The bands on which each brand's own printed chart lists this cup. A chart check, not a stock check.
| Brand | UK A (1 in) |
|---|---|
| Elomi | not on its chart |
| Freya | not on its chart |
| Marks & Spencer | 28 to 44 |
| Victoria's Secret | 30 to 44 |
| The Little Bra Company | 28 to 38 |
| ThirdLove | 32 to 44 |
Elomi: US underband and cup sizing, 32 to 48 bands and B to O cups (UK B to K; its chart continues to UK KK). Freya: bands 28 to 44, UK cups B to K. Marks & Spencer: its UK row lists sizes from 28AA to 46K (no FF, HH or JJ); matched here by the label as printed. Victoria's Secret: international chart: bands 30 to 44, AA to DDD (UK E). The Little Bra Company: its size picker: bands 28 to 38, cups AA to D (a specialist for small sizes). ThirdLove: bands 32 to 44, AA to H in US letters (UK FF), plus half cups.
What is particular about the A cup
AA is the step below, not another name
An AA cup is zero inches of difference (bust equal to band) and an A is one. Every country's ladder in our chart starts at AA except Japan's, whose first letter is A: its A is our AA and its B is our A.
An old calculator can call a DD an A
A 34 in underbust with a 39 in bust measures 34DD. The +4 method pads the band to 38 and takes the cup from 39 - 38 = 1 in, so it prints 38A. In the other direction, a true A cup gets no letter at all: 34 in and 35 in measure 34A, and +4 answers "38 (below AA)". If an old calculator told you an A, measure again.
Marks & Spencer's US column moves it by band
On the M&S US size guide a UK 32A keeps its letter (US 32A) but a UK 34A is a US 34AA, one letter lower than every other chart we read. Buying M&S from the US, go by the UK label.
Not every chart starts at A
Freya's and Elomi's printed ranges begin at B, so an A cup is not on either chart. The Little Bra Company, a specialist for small sizes, offers AA to D on bands 28 to 38. The table below lists the bands each chart covers.
Other sizes and tools
- Bra size calculatorMeasure your size with both methods shown
- UK to US converterAny size in any of six systems
- Sister size chartThe full diagonal chart and fit fixes
- B cupWhat the letter means, by band
- D cupWhat the letter means, by band
- DD cupWhat the letter means, by band
- E cupWhat the letter means, by band
Sources
Each source was opened and checked on the date shown, or on 25 September 2026. Where sources disagree, the page says so instead of picking one silently.
- Wikipedia, "Bra size": UK and US cup ladders, the +4 method, EN 13402 and JIS cup steps
- White J, Scurr J. Evaluation of professional bra fitting criteria for bra selection and fitting in the UK. Ergonomics 2012;55(6):704-711: 45 women; the traditional method overestimated band and underestimated cup
- Marks & Spencer US, "Bras size guide": UK, AU/NZ, US/CA, EU and FR conversion table (opened 26 September 2026)
- Victoria's Secret Customer Care, "Size & Fit: International Size Chart (Outside the U.S.)": US sizes sold; bands 30 to 44, cups AA to DDD; US DDD = UK E (opened 26 September 2026)
- ThirdLove, "Bra Size Calculator & Chart": bands 32 to 44, cups AA to H with half cups; calculator run with 6 measurement pairs (opened 26 September 2026)
- Freya, "International Bra Size Chart & Bra Sizing": band and cup tables in UK, EU, FR, AU/NZ, US and JP (opened 26 September 2026)
- Elomi, "International Size Guide": US underband and cup sizing, B to O cups and 32 to 48 bands; UK, EU, FR, AU/NZ, US and JP rows (UK cups to KK, US to P) (opened 29 September 2026)
- The Little Bra Company, "Fit Calculator": its size picker offers bands 28 to 38 and cups AA to D (opened 29 September 2026)
- Wacoal America, "Size Charts": US and UK cup ladders side by side (opened 26 September 2026)