D cup size: what it means, and why it changes by band
D is four inches of difference between bust and band. It is not "a large cup": our own 30D, 34D and 38D pages are three different bodies that all carry a D letter.
D cup by band, in every system
| UK | US | EU | FR | AU | JP (approx.) |
|---|---|---|---|---|---|
| 30D | 30D | 65D | 80D | 8D | E65 |
| 32D | 32D | 70D | 85D | 10D | E70 |
| 34D | 34D | 75D | 90D | 12D | E75 |
| 36D | 36D | 80D | 95D | 14D | E80 |
| 38D | 38D | 85D | 100D | 16D | E85 |
| 40D | 40D | 90D | 105D | 18D | E90 |
"d cup size" gets about 14,800 Google searches a month in the US (Google Ads data, 26 September 2026).
Sister sizes keep the D cup's volume
Go down one band and up one letter, or up one band and down one letter, and the cup volume stays the same.
| UK | US | Compared with 30D |
|---|---|---|
| 28DD | 28DD | Tighter band, 1 letter up |
| 30D | 30D | This size |
| 32C | 32C | Looser band, 1 letter down |
The full diagonal chart, with fit fixes for a band that rides up or digs in, is on the sister sizes page.
What people get wrong about the D cup
D is not automatically a large cup
The same one-inch step separates every letter on the ladder. Our 30D, 34D and 38D pages measure roughly 30/34 in, 34/38 in and 38/42 in underbust and bust: three different bodies, the same D letter, because each is exactly four inches of difference on its own band.
The +4 method treats a D cup very differently depending on the band
On a 30 in underbust and 34 in bust (30D on the measured-band method), the traditional +4 method returns 34AA. On a 38 in underbust and 42 in bust (38D), it returns 42AA. Same padded-band pattern both times, the direction White and Scurr (2012) measured in UK fittings.
Other sizes and tools
- Bra size calculatorMeasure your size with both methods shown
- Sister size chartThe full diagonal chart and fit fixes
- 30DSister sizes, conversions and the measurements that land on 30D
- 34DSister sizes, conversions and the measurements that land on 34D
- 38DSister sizes, conversions and the measurements that land on 38D
- B cupWhat the letter means, by band
- DD cupWhat the letter means, by band
- E cupWhat the letter means, by band
Sources
Each source was opened and checked on 25 September 2026. Where sources disagree, the page says so instead of picking one silently.
- Wikipedia, "Bra size": UK and US cup ladders, the +4 method, EN 13402 and JIS cup steps
- White J, Scurr J. Evaluation of professional bra fitting criteria for bra selection and fitting in the UK. Ergonomics 2012;55(6):704-711: 45 women; the traditional method overestimated band and underestimated cup