Bra Size Chart: Band and Cup Conversions Across US, UK, EU and AU Size Runs
Band comes from the snug underbust measurement rounded to the nearest even inch — 81 cm is a 34, and the same rib cage is a 75 in Germany, a 90 in France and a 14 in Australia. Cup comes from the difference between the bust measurement and that band, at roughly 2.5 cm per letter. The four systems agree perfectly up to D and then split, which is why one body is legitimately a 34DD, a 34E and a 75F at the same time.
By the Think Bra Editorial Team
Two numbers produce a size. Measure snug around the rib cage directly under the bust — that sets the band. Measure across the fullest point of the bust with no tension on the tape — the difference between that figure and your band, counted in inches, sets the cup. One inch is an A. Four is a D. Eight is a UK FF, a US H and a continental H.
Everything past the letter D is where the systems come apart, and they come apart badly. A body measuring 76 cm under the bust and 97 cm across it has a 32 band and an eight-inch difference. In a UK run that is 32FF. In a US run it is 32H. In a German or Belgian run it is 70H. In Australia it is 12G. Four labels, one body, no error anywhere.
The reason is structural rather than sloppy. Nobody governs bra sizing. There is no ISO standard, no trading-standards definition, no legal meaning attached to the letter on the tag. A cup letter is an ordinal position inside one manufacturer's grading run, and different regions built their runs on different alphabets — the UK doubles letters (DD, FF, GG, HH), the US inserts DDD, and the Continent runs straight through the alphabet with no doubles at all. Same physical volume, different position in the alphabet, different letter printed on the label.
The tables below convert between all four. Take your own two measurements first, then read across.
Band conversions: one rib cage, four numbers
Band is the easy half. Take the snug underbust measurement, round it to the nearest even inch, and that is your band in the US and UK systems. Everything else is arithmetic on that figure.
The right-hand column is there as a warning. It shows what the legacy add-four-inches rule would have printed on your label — a rule that still sits inside a lot of brand calculators and a great many third-party ones.
Band (US / UK) Snug underbust — inches Snug underbust — cm EU (DE / NL / SE / IT) FR / ES / BE AU / NZ What the legacy +4 rule would call it 28 26 – 28 66 – 71 60 75 8 32 30 28 – 30 71 – 76 65 80 10 34 32 30 – 32 76 – 81 70 85 12 36 34 32 – 34 81 – 86 75 90 14 38 36 34 – 36 86 – 91 80 95 16 40 38 36 – 38 91 – 97 85 100 18 42 40 38 – 40 97 – 102 90 105 20 44 42 40 – 42 102 – 107 95 110 22 46 44 42 – 44 107 – 112 100 115 24 48 46 44 – 46 112 – 117 105 120 26 50 48 46 – 48 117 – 122 110 125 28 52 Find your snug underbust in the inches or cm column, then read your band number in whichever system the garment is labelled in. The final column is the number to ignore, not the number to use. The three conversions are all fixed relationships, so you can do them in your head once you have seen them. EU cm band = US band multiplied by 2.5, minus 10. FR band = EU band plus 15. AU band = US band minus 20. There is no ambiguity in any of them and no brand deviates.
Bands below 28 and above 48 exist but thin out fast. A 26 band is made by a handful of UK and Polish specialists. Above 48 you are into a small number of US plus-size runs, and the letters those runs use stop mapping cleanly onto anything else.
What each inch of difference is called, in four alphabets
Cup is the difference between your bust measurement and your band number, not between your bust and your raw underbust. Get that wrong by one step and every letter below shifts.
One inch equals 2.54 cm, and in the UK and US runs one inch equals one cup step. Continental runs are drafted in centimetres, and while most published conversion tables treat a continental letter as equivalent to one inch of difference, several Polish and German runs step at roughly 2 cm instead. That single half-centimetre discrepancy is why a conversion that is exact at C is half a letter out by G.
Bust minus band (in) Difference (cm) UK US EU / FR / BE AU / NZ (most common run) Where the systems part company 0 0 AA AA AA AA All four agree 1 2.5 A A A A All four agree 2 5.1 B B B B All four agree 3 7.6 C C C C All four agree 4 10.2 D D D D Last coordinate at which all four print the same letter 5 12.7 DD DD E DD The Continent steps to E while the UK, US and AU double the D 6 15.2 E DDD F E The letter E now means 15 cm in the UK and 12.7 cm on the Continent 7 17.8 F G G F US runs jump from DDD to G; some print DDDD instead 8 20.3 FF H H G AU drops the doubled letters here and stops tracking the UK 9 22.9 G I I H Several US makers omit I entirely and go DDD, G, H, J 10 25.4 GG J J I UK G and US J are the same volume — nothing in the letters says so 11 27.9 H K K J Four systems, four different letters, one body 12 30.5 HH L L K UK doubling is now two full letters behind the Continental run 13 33.0 J M M L UK skips I altogether to avoid confusion with the numeral 14 35.6 JJ N N M Above here, published cross-brand conversions stop agreeing with each other 15 38.1 K O O N Very few runs reach this coordinate; treat any conversion as provisional Work out your difference in whole inches, find the row, and read the letter for whichever system the garment uses. If a size chart does not say which system it is written in, the letter tells you nothing. The Australian column carries a caveat the other three do not. There is no single Australian run — the major Australian and New Zealand labels broadly share band numbering but split on cup lettering above E, with some dropping the doubled letters and others keeping DD and then running straight. Check the brand's own chart rather than assuming AU means UK-minus-doubles.
The US column carries its own oddity. A run that goes A, B, C, D, DD, DDD, G, H, J has silently skipped I, which means a shopper counting letters upward from DDD lands one full cup letter short. It is not a typo and it is not rare.
The E problem, and why it causes most of the confusion
One letter causes more mis-sizing than the rest of the alphabet combined. In a UK run, E sits at six inches of difference. In a continental run, E sits at five. A UK E and a German E are one full cup letter apart in volume, and both are printed as the single character E.
Play that through. A wearer measures a five-inch difference, buys a UK DD that works, then orders from a Belgian label and picks E because a chart told her DD equals E. That chart was right. She now has a continental E, which is the same volume as her UK DD, and it works. Fine. Next season she orders from a UK label and picks E because the last one said E — and she has jumped a full cup letter without noticing.
The same trap runs at every coordinate above D. US DDD and UK E are equivalent. UK F and US G are equivalent. UK FF and US H are equivalent. None of those pairings is guessable from the letters, and none of them is written on the garment.
Treat the letter as a coordinate that only means something once you know which grid it belongs to. If a listing says "34F" with no country of origin, that garment is either a six-inch cup or a seven-inch cup, and you cannot tell which.
Worked examples: eight bodies through all four systems
Each row below starts from two real tape measurements and runs them out to the size printed in each system. Nothing in the row changes except the alphabet.
Snug underbust Bust (leaning forward) Band Difference UK US EU AU 30 in / 76 cm 35 in / 89 cm 30 5 in / 12.7 cm 30DD 30DD 65E 10DD 32 in / 81 cm 40 in / 102 cm 32 8 in / 20.3 cm 32FF 32H 70H 12G 34 in / 86 cm 40 in / 102 cm 34 6 in / 15.2 cm 34E 34DDD 75F 14E 28 in / 71 cm 37 in / 94 cm 28 9 in / 22.9 cm 28G 28I 60I 8H 36 in / 91 cm 40 in / 102 cm 36 4 in / 10.2 cm 36D 36D 80D 16D 38 in / 97 cm 45 in / 114 cm 38 7 in / 17.8 cm 38F 38G 85G 18F 42 in / 107 cm 53 in / 135 cm 42 11 in / 27.9 cm 42H 42K 95K 22J 44 in / 112 cm 57 in / 145 cm 44 13 in / 33.0 cm 44J 44M 100M 24L Read the row that matches your two measurements, then use the column for whichever market you are ordering from. Copy the whole row into your phone notes — you will need all four. Notice how little the letters resemble each other by the time you reach row seven. A 42H, a 42K, a 95K and a 22J are the same garment volume on the same rib cage. Somebody who knows she is a 42H and reads a US chart offering DD as its top size will conclude, reasonably and wrongly, that the range does not go big enough — when in fact it never had a coordinate for her at all.
Half-inches, odd numbers and coordinates that do not exist
Measurements do not politely land on whole numbers. Three situations come up constantly.
A difference that lands on a half-inch. You measure 6.5 inches and sit between UK E and F. Take the larger letter in an unlined or stretch-lace cup, which will take up the slack, and the smaller letter in a moulded or foam cup, which will not. A half-inch of unfilled moulded cup wrinkles at the apex and is visible under clothing; a half-inch of unfilled stretch lace disappears.
An odd underbust measurement. You measure 33 inches and sit between a 32 and a 34 band. Firm, muscular rib cages take the larger band; softer tissue that compresses under the tape takes the smaller one. If you have both a snug and a relaxed underbust figure and they differ by more than about 4 cm, that tissue is soft — size down.
A coordinate the brand simply does not make. A run that stops at DDD has no coordinate at all for a nine-inch difference, and there is no way to reach it with sister sizing. It is not a size problem, it is an inventory problem, and the answer is a different manufacturer.
Half-cup sizing exists in a small number of US ranges — a half-letter step between the whole letters, giving a genuinely finer grade. It solves the first problem elegantly and creates a new one: a half-cup coordinate has no equivalent in any other run on earth. Convert to the nearest whole letter and accept half a step of error.
Why the chart is a starting point rather than an answer
This chart converts between systems. It does not convert between manufacturers, and those are different problems.
Two labels can both be genuinely, correctly UK-lettered and still put you in different sizes, because each grades its range outward from its own base fit block, applies its own band rule, and chooses its own cup depth and wire width at every coordinate. A 34F drafted with a deep, projected cup and a 34F drafted with a shallow, wide cup hold roughly the same volume distributed completely differently, and only one of them will work on a given body.
So use the chart to get to a starting coordinate, then expect to move. Two moves cover most of it: sister sizing, which swaps band for cup while holding the volume constant, and the per-brand offset, which tells you how far a particular run sits from the reference standard before you order anything.
One habit is worth building. Whenever a bra works, write down the brand, the style name, the size and the system it was labelled in. That record is more useful than any chart, because it is the only measurement you will ever have of a garment that actually held.
The rules, condensed
- Band = snug underbust in inches, rounded to the nearest even number. Nothing gets added.
- Cup = bust measurement minus band number, at one letter per inch (2.54 cm).
- EU cm band = (US band × 2.5) − 10. FR band = EU band + 15. AU band = US band − 20.
- All four systems agree up to and including D. Above D, always establish which grid the letter belongs to.
- UK doubles letters (DD, FF, GG, HH, JJ) and skips I. US inserts DDD and often skips I. The Continent runs straight through with no doubles.
- UK DD = US DD = EU E. UK E = US DDD = EU F. UK F = US G = EU G. UK FF = US H = EU H.
- A chart that adds four or five inches to your underbust is calibrated to a garment made before stretch elastic existed. Ignore it.
- If a size chart does not name the system it is written in, the letters on it carry no information.