Bra Size Converter

UK, US, EU, French, Italian, Japanese and Australian bra sizes, both parts converted separately — because the band converts by arithmetic and the cup does not. Above a D the letter sequences diverge, so a UK 34F is not a US 34F, and this page says which is which.

The band is arithmetic; the cup is a table

Bands, seven countries, and the measurement behind them

Cups: one step, four different letters

Sister sizes around a 34D

A UK 34F is not a US 34F

A bra size is two measurements wearing one label, and they behave completely differently when you cross a border. The band is a length. Britain and America print it in inches; Germany, Scandinavia and Japan print the under-bust in centimetres; France, Spain and Belgium print the same centimetre number plus fifteen; Italy prints a small ordinal; Australia prints the British number minus twenty-two. All of those are arithmetic, all of them are reversible, and this page reproduces the published European column exactly from the under-bust — which is how you can tell the international charts are built on the old “add four inches” fitting method rather than on a snug under-bust.

The cup is not a length, it is a position in a list of letters, and the lists differ. Up to D everyone agrees. After that Britain runs DD, E, F, FF, G, GG, H, HH, J; America runs DD, DDD (sometimes printed F), G, H, I, J, K; Europe runs D, E, F, G, H with no doubled letters at all. One physical cup — six inches of difference between bust and band — is a British E, an American DDD and a European F. So the single most useful sentence on this page is: a UK 34F is a US 34G, and an American 34F is a British 34E. Two eBay listings of the same garment in two markets say exactly that: “UK SIZE 34E / US SIZE 34DDD” and “UK SIZE 34F / US SIZE 34G”.

How to measure, since the size is derived rather than printed on you. Two figures: the under-bust, taken snug and level directly under the bust while breathing out, and the over-bust, taken round the fullest part standing upright with the tape level and not pulled in. The band comes from the first and the cup from the difference between them — one letter per inch, 2.54 cm. The honest complication is that British fitters today often take the band as the snug under-bust in inches, which lands two to four bands lower and correspondingly more cups up than the method the conversion charts embed. Both are in use. Neither is arithmetically wrong; they are different fitting philosophies, and this page tells you which one it is using rather than pretending there is one answer.

Sister sizing is the practical trick. Going down one band and up one cup — a 34D to a 32DD — keeps the cup about the same and tightens the frame; going up a band and down a cup does the reverse. That is the move when your size is out of stock, and the table above gives the whole ladder around a 34D with each rung’s measurements. It is not a free substitution: the band is doing the support, so a band two sizes off will sit differently even with the right cup.

Finally, the usual warning, and it bites harder here than anywhere. Bra sizing charts are makers’ conventions. The same printed size differs between brands, between ranges within a brand and between cuts within a range, and cup shape matters as much as cup volume. Use this page to know which letter to look for, then try the garment. For the other sizing scales that work the same way — a convention on top of a measurement — see the clothing size converter and the shoe size converter. This page does the arithmetic. Where the answer carries a consequence — a dose, a structural load, a legal area, a medical measure — confirm it against the authority that governs it before relying on it.

Frequently asked questions

Related calculators

References

1. HauteFlair, Bra Size Conversion Chart (read 26 September 2026): the band table used here — US and UK in inches, EU and Japan at 2.5 times the UK number less ten, France and Spain fifteen above the EU number, Italy at half the UK number less fifteen, Australia twenty-two below the UK number — and the cup positions for the US, UK, EU and Australian letter sequences.
2. erlich textil, Bra Size Conversion: EU, US & UK Chart (read 26 September 2026), an independent check on the band table: EU 70 to UK 32, EU 75 to UK 34 and so on, with the rule stated as five centimetres of EU band to two inches of UK band, and the observation that the cup letters only start to diverge at the EU E cup.
3. The Bra Diva, UK to US Bra Size Chart: Cup Letters After DD (read 26 September 2026), for the two letter sequences past DD: UK DD, E, F, FF, G, GG, H, HH, J, JJ against US DD, DDD/F, G, H, I, J, K, L, M, N. It also notes that UK sizing skips the letter I where US sizing uses it.
4. aimerfeel, Japanese bra size, explained (read 26 September 2026), a Japanese lingerie retailer’s own guide. It gives the Japanese band as the under-bust in centimetres and its cups as roughly 2.5 cm steps of top-bust minus under-bust, and it advises Western customers to go up a cup — two above a US E — which is direct evidence that the letter-for-letter conversion in the charts is approximate.
5. EN 13402-3, Size designation of clothes — Body measurements and intervals, the European standard behind the continental size numbers. Copyrighted and cited by number only. What this page uses is the published definition of the German Konfektionsgröße that follows it: a man’s jacket size is half his chest circumference in centimetres, and a woman’s dress size is half her bust circumference in centimetres minus six.