US and UK bands use the same inch scale, so the band number doesn’t change at all — a US 34 is a UK 34. Cups match through D, then a US DD is a UK DD too, but a US DDD is a UK E and a US G is a UK F.
This is the simplest half of any bra conversion: US and UK band sizes are the same inch measurement, so the number carries over unchanged — US 30 is UK 30, US 38 is UK 38, with nothing to look up beyond confirming the band itself.
Cup letters are where the two systems part ways, and not at the same point you might expect: US and UK both use DD for the size right after D. Past that, though, they diverge — a US DDD is a UK E, a US G is a UK F, and a US H is a UK FF. Some US brands relabel DDD as F and G as DDDD, which this converter also accounts for.
| Band (US) | Band (UK) |
|---|---|
| 28 | 28 |
| 30 | 30 |
| 32 | 32 |
| 34 | 34 |
| 36 | 36 |
| 38 | 38 |
| 40 | 40 |
| 42 | 42 |
| 44 | 44 |
| Cup (US) | Cup (UK) |
|---|---|
| AA | AA |
| A | A |
| B | B |
| C | C |
| D | D |
| DD / E | DD |
| DDD / F | E |
| G / DDDD | F |
| H | FF |
| I | G |
| J | GG |
| K | H |
Cup letters match through D; above D the systems diverge, which is why the cup half of this chart is a lookup, never a formula.
No — US and UK bra bands use the identical inch scale, so a US 32 is a UK 32, a US 36 is a UK 36, and so on.
Yes, DD is one of the few cup letters that matches exactly between US and UK. The divergence starts at the next size up.
A US DDD (sometimes labelled F by US brands) converts to a UK E.