Quick answer: An under-bust of 76 cm and a bust of 92 cm give band 75 and a 16 cm difference, which is cup C: EU 75C, UK and US 34C.
How it's calculated
European sizes follow the standard EN 13402: the band is the under-bust girth rounded to the nearest 5 cm (70, 75, 80 …), and the cup comes from the difference between bust and under-bust in 2 cm steps: 10–12 cm is AA, 12–14 cm A, 14–16 cm B, 16–18 cm C and so on.
UK and US labels use the usual conversion from EU sizes: band 65 = 30, 70 = 32, 75 = 34, 80 = 36. Cups match up to D; after that UK uses DD, E, F, FF, G and US uses DD, DDD, G, H. French bands are the EU band + 15. Some calculators instead take the under-bust in inches as the UK band and count one cup per inch, which gives a smaller band and a bigger cup letter (for 76/92 cm about 30E rather than 34C); try both if a size fits badly.
Measure without a padded bra, keep the tape level and snug for the under-bust, loose around the fullest part for the bust. Measurements in inches are converted to cm first (1 in = 2.54 cm).
Worked examples
- Under-bust 76 cm, bust 92 cm: band 75, 92 − 76 = 16 cm → EU 75C, UK 34C
- Under-bust 82 cm, bust 102 cm: band 80, 20 cm → EU 80E, UK 36DD, US 36DD
- Under-bust 30 in, bust 36 in: 76.2 cm, 91.4 cm → 15.2 cm → EU 75B
Cup by bust − under-bust (cm)
| Difference (cm) | EU | UK | US |
|---|---|---|---|
| 12–14 | A | A | A |
| 14–16 | B | B | B |
| 16–18 | C | C | C |
| 18–20 | D | D | D |
| 20–22 | E | DD | DD |
| 22–24 | F | E | DDD |
| 24–26 | G | F | G |
| 26–28 | H | FF | H |
Frequently asked questions
Why does my size differ between shops?
Brands cut differently and some still use older methods (adding inches to the band). Treat the calculated size as a starting point and try a size up or down in the band or cup.
What are sister sizes?
Sizes with the same cup volume: going one band up and one cup down (75C → 80B) or one band down and one cup up (75C → 70D).
Should I measure in cm or inches?
Either. Centimetres match the EU standard directly; inches are converted to cm before the size is worked out.
How often should I measure again?
About once a year, and any time your weight changes noticeably or after pregnancy and breastfeeding. Your size moves with your body.
Which matters more for fit, the band or the cup?
The band. It does most of the supporting, so on a new bra it should sit level and feel snug on the loosest hook. If the band's right but the cup gaps or spills over, change only the cup.
Why is my cup letter bigger than I expected?
Because cup letters are tied to the band. A C cup on a 70 band is smaller than a C cup on an 85 band, so a bigger letter on a smaller band is perfectly normal.