Bra size converter
Translate a bra label between the UK, US, European, French, Australian and Japanese systems, see its sister sizes, or work out a starting size from two measurements, with an honest word on why bra sizes rarely line up.
UK 34C in other countries
- UK34C
- US34C
- EU75C
- FR / BE / ES90C
- AU / NZ12C
- JPD75
Sister sizes in UK
- Tighter band, larger cup
- 32D 30DD
- Looser band, smaller cup
- 36B 38A
Under the European rule (EN 13402) this label is made for an underbust of about 73–77 cm and a bust about 89–95 cm. Japanese letters are matched by the bust-minus-underbust difference, because JIS cups grow in 2.5 cm steps instead of 2 cm.
Above a G cup, brands disagree: some European labels skip the letter I, and US brands vary after DD (DDD, E or F). Check the brand's own chart for large cups.
Sister-size grid
Your size in yellow; its sister sizes run along the diagonal.
| Band | A | B | C | D | DD | E | F | FF | G | GG |
|---|---|---|---|---|---|---|---|---|---|---|
| 30 | 30A | 30B | 30C | 30D | 30DD | 30E | 30F | 30FF | 30G | 30GG |
| 32 | 32A | 32B | 32C | 32D | 32DD | 32E | 32F | 32FF | 32G | 32GG |
| 34 | 34A | 34B | 34C | 34D | 34DD | 34E | 34F | 34FF | 34G | 34GG |
| 36 | 36A | 36B | 36C | 36D | 36DD | 36E | 36F | 36FF | 36G | 36GG |
| 38 | 38A | 38B | 38C | 38D | 38DD | 38E | 38F | 38FF | 38G | 38GG |
| 40 | 40A | 40B | 40C | 40D | 40DD | 40E | 40F | 40FF | 40G | 40GG |
| 42 | 42A | 42B | 42C | 42D | 42DD | 42E | 42F | 42FF | 42G | 42GG |
| 44 | 44A | 44B | 44C | 44D | 44DD | 44E | 44F | 44FF | 44G | 44GG |
| 46 | 46A | 46B | 46C | 46D | 46DD | 46E | 46F | 46FF | 46G | 46GG |
How to use it
A bra size: choose the country on the label, then its band and cup. You get the same label in the other five systems and the sister sizes. My measurements: enter a snug underbust and a loose bust in centimetres or inches. The table shows the starting size each country's own rule gives.
What the systems mean
- UK and US bands are in inches (32, 34) and cups grow by one letter per inch of bust over the band. The UK uses DD, FF, GG; US brands mostly go DD, DDD, G.
- EU (EN 13402) bands are the underbust in centimetres, rounded to 5 (70, 75); cups grow every 2 cm, starting with A at 12–14 cm.
- FR / BE / ES add 15 to the European band (70 becomes 85). AU / NZ bands are the UK band minus 22 (32 becomes 10).
- Japan (JIS L 4006) writes the cup first (C70) and steps cups every 2.5 cm.
Sister sizes keep about the same cup volume on a different band: go one band down and one cup up (34C to 32D), or the reverse. They help when a band feels loose or tight but the cups fit.
Worked example: UK 34C is US 34C, EU 75C, French 90C, Australian 12C and about D75 in Japan. Its sister sizes are 32D and 36B.
Sources
- Bra size (Wikipedia): band equivalents between systems (UK 32 = EU 70 = FR 85 = AU 10), the EN 13402 cup table (A = 12–14 cm), JIS L 4006 and KS K 9404 cups in 2.5 cm steps, French bands at European + 15, UK and US cup letter sequences and the measuring methods.
- CEN, EN 13402: Size designation of clothes, summarised in EN 13402 (Wikipedia): the European bra size label (for example 70B).
- Japanese Standards Association, JIS L 4006 Sizing systems for foundation garments: Japanese band and cup designation.
Questions
What are sister sizes?
Sizes with roughly the same cup volume on a different band. One band down and one cup up (34C to 32D) keeps the cup about the same on a tighter band; one band up and one cup down (34C to 36B) does the reverse. They are useful when the cups fit but the band does not.
Why does my measured UK size not match my measured EU size?
The two systems count differently. The UK method rounds the underbust to an even number of inches and adds a cup for each inch of bust above that band; the European method rounds the underbust to 5 cm and adds a cup for every 2 cm above the underbust itself. Both are legitimate starting points; use the one the brand's own chart uses.
Is a US DDD the same as a UK E?
On most labels, yes: US DD/E = UK DD = EU E, and US DDD/F = UK E = EU F. Above that, US brands mostly continue G, H, I while UK brands use F, FF, G, GG. Some US brands call DDD an F, so check the brand's chart for larger cups.
Why do Japanese sizes read C70 instead of 70C?
JIS L 4006 writes the cup letter first. Japanese cups also grow in 2.5 cm steps from AA at 7.5 cm, so for small and medium cups the Japanese letter is often one letter larger than the European one for the same body.
Should I trust my measurements or the fit?
The fit. Measurements give a starting size; breast shape, the style of the bra and how firmly a brand cuts its bands all move the result by a size or more. Try the starting size and its sister sizes, and use the fit check above.
When should I measure again?
Whenever bras start to fit differently: after a change in weight, during and after pregnancy and breastfeeding, with new training routines, or simply when a favourite size stops feeling right.