Bra size conversion confuses shoppers because it is really two conversions wearing one coat. The band converts by arithmetic — each system numbers the same ribcage differently. The cup converts by table — each system assigns its letters to the same inch differences differently. This page is a complete bra size converter in print: the bra conversion chart for bands, the cup table, and worked conversions checked against the calculator, so a bra size conversion never has to be a guess again.

Band conversion: one ribcage, five numberings

The UK keeps the US band number exactly. The EU (German) band is a centimetre-based dress size: US band × 2.5, minus 10. French and Spanish sizes add 15 to the EU figure. Italian sizes count upward from 1 in steps that match the EU table. Australian sizes are dress sizes: the US band minus 22. An international bra size converter is, for bands, just those four sums:

Check the anchor everyone knows: a US 34 band is a UK 34, an EU 75, a French 90, an Italian 3 and an Australian 12. If a brand’s chart disagrees with the table by a step, the brand is grading on its own convention — possible, but the table is the standard the calculator uses.

Cup conversion: same inches, different alphabets

All three systems below measure the cup the same way — bust minus band, in inches — and then name the result differently. The US inserts DD and DDD; the UK inserts DD, then continues E, F, FF, GG; the EU runs single letters straight through with no doubles at all:

Two consequences follow. First, uk bra size to us conversion is safe up to a D cup and treacherous after it: a UK E is not an American E (US sizing has no plain E at that step — it is a DDD). Second, going the other way, uk to us bra size conversion of a GG or HH has no tidy US letter at all in many brands’ ranges, which is why large-cup shoppers often buy by the UK label regardless of where they live.

Worked conversions

US 34D. Band: UK 34, EU 75, FR 90, IT 3, AU 12. Cup: a 4-inch difference is D in all three alphabets. Full set: UK 34D · EU 75D · FR 90D · IT 3D · AU 12D.

US 38DD. Band: UK 38, EU 85, FR 100, IT 5, AU 16. Cup: a 5-inch difference is DD in the US and UK, but E in the EU’s single-letter run. Full set: UK 38DD · EU 85E · FR 100E · IT 5E · AU 16DD.

US 30DDD. Band: UK 30, EU 65, FR 80, IT 1, AU 8. Cup: a 6-inch difference is DDD in the US, E in the UK, F in the EU — three labels, one measurement. Full set: UK 30E · EU 65F · FR 80F · IT 1F · AU 8DDD.

Where conversions stop working

Three honest limits. Brand grading: the tables convert the systems, not individual brands, and brands cut the same label differently — a converted size is a starting size, and the fit check has the final word. The +4 legacy: a minority of brands still grade bands on the older add-4-inches convention, so their 34 fits like another brand’s 32; if a converted size’s band feels a size off in both directions of a brand’s range, that is usually why. Half steps and extremes: at the smallest bands and largest cups, some systems simply stop printing labels, and the calculator flags those results as extrapolated for exactly that reason.

Convert the band by formula and the cup by table, and uk bra sizes stop being a foreign language: they are your size, spelled in another system.

Beyond the big four: Japanese and Korean sizes

The calculator’s results panel also prints Japanese and Korean equivalents, and both are simpler than they look: they use the EU band number with the EU-style single-letter cup. A US 34D is a Japanese 75D and a Korean 75D — the same figures as the EU row. The trap is assuming the letter D means the conversion is finished: at a 5-inch difference the Japanese size is 75E where the US label says DD, following the EU alphabet exactly. Convert JP and KR sizes with the EU column of both tables and you will not go wrong.

Converting backwards: from a foreign label to your US size

Conversion runs both ways, and the reverse direction is where shoppers actually get stuck, holding a European tag in a US shop. Work it in reverse order: band first, cup second. The band: add 10 to the EU figure and divide by 2.5 — an EU 85 becomes (85 + 10) ÷ 2.5 = 38. The cup: find the EU letter in the difference table and read its inch value — E is a 5-inch difference — then take the US letter for that difference: DD. So an EU 85E is a US 38DD, which matches the forward conversion of 38DD earlier on this page, as it must: a correct converter is a round trip.

One more round trip, in full. A US 32C: band — UK 32, EU 70, FR 85, IT 2, AU 10; cup — a 3-inch difference is C in all three alphabets. And back again: an AU 10 is a US band of 10 + 22 = 32, and its C is a 3-inch difference, a US C. If your round trip does not return you to your starting size, the error is in the cup table step almost every time — the alphabets, not the arithmetic.

The four conversion mistakes

Converting the letter by alphabet. “E comes after D” is not a conversion; the US has no plain E at the 5-inch step (it is DD) and the UK’s E is the US DDD. Always route through the inch difference. Forgetting the AU band is a dress size. An Australian 12 is not a small bra — it is a US 34 band, because the AU number counts clothing sizes, not inches. Converting a +4-graded brand by the standard table. Brands that grade on the old add-4 convention cut their bands a size small against these tables; the table converts systems, and a brand’s private convention rides on top. Trusting a converted size over the fit check. The conversion gives you the size to try first, in a shop whose labels speak another system. The five fit checks — level band, tacking gore, no spill, no wrinkle, quiet straps — remain the verdict in every country and every alphabet.

None of this requires talent for numbers. It requires refusing to convert the one thing that does not convert — the letter — and always converting the two things that do: the band, by formula, and the difference, by table.

Quick reference: the sizes met most often, fully converted

For the sizes that come up constantly, here is the whole conversion done at once — each row generated by the same formulas and tables as the worked examples:

A warning about the EU number: it is not a measurement

Shoppers who measure in centimetres often try to read the EU band as a centimetre figure, and it cannot be done: the EU number is a dress size, not a tape reading. A US 34 band corresponds to an underbust of 34 inches — about 86 cm — yet its EU label says 75. The 75 comes from the conversion formula (34 × 2.5 − 10), not from any circumference on your body. If your underbust measures 86 cm, your route to an EU size runs through the inches first: 86 cm is a 34 band, and the 34 band is an EU 75. Skipping the middle step and shopping for a “size 85” buys a band two sizes too big — the single most common conversion error among centimetre measurers, and the reason this page converts bands by formula rather than by unit.

Two more, at the edges of the everyday range. A US 36DDD: band — UK 36, EU 80, FR 95, IT 4, AU 14; cup — a 6-inch difference, UK E and EU F: 36E · 80F · 95F · 4F · 14DDD. A US 42B: band — UK 42, EU 95, FR 110, IT 7, AU 20; cup — a 2-inch difference is B everywhere: 42B · 95B · 110B · 7B · 20B. Notice what the edges teach: the band numbers drift furthest apart exactly where the cup letters agree (42B), and the letters split exactly where the bands agree (36DDD). The two conversions really are independent, at every size.