Bra Size Calculator · Practical guide
US vs UK Bra Size Conversion
Band sizes are the same on both sides of the Atlantic — the differences live in the cup letters.
At a glance
The Simple Version
For most sizes, converting between US and UK bra sizing is a non-event: band sizes are identical, and in the standard conversion used by this calculator, cup letters match from AA all the way through G. A 34C in US sizing is a 34C in UK sizing. Where the two systems can diverge is beyond DD — some brands label US DDD where a UK brand uses E — so always check the size chart when shopping a new label, especially in fuller cups.
Interactive tool
Bra Size Calculator
Enter your own values, then compare the result with the examples below.
Results
US to UK Conversion Table
| Bust − Band Difference | US Cup | UK Cup |
|---|---|---|
| 0 in | AA | AA |
| 1 in | A | A |
| 2 in | B | B |
| 3 in | C | C |
| 4 in | D | D |
| 5 in | DD | DD |
| 6 in | E | E |
| 7 in | F | F |
| 8 in | G | G |
Why Conversions Get Confusing
There is no single enforced international standard, so individual brands improvise past a DD cup. One label's US DDD is another's US F; UK brands often continue with E, F, FF, G, GG. European (EU) sizing adds a third system that numbers bands in centimeters instead of inches — a US/UK 34 band is roughly an EU 75. The calculator above reports the standard US and UK equivalents side by side so you can compare directly.
Worked Example
Take an under-bust of 36 inches and a bust of 43 inches. The band stays 36 and the 7-inch difference maps to an F cup. This calculator reports US 36F and UK 36F. If a particular UK brand runs one letter higher past F, its chart might call that a 36E — a good reminder that the measured size is a starting point, and the brand's own chart is the tiebreaker.
Frequently Asked Questions
Do US and UK band sizes differ?
No. A 34 band is a 34 band in both systems — both use the under-bust measurement in inches rounded to the nearest even number.
Where do US and UK cup sizes stop matching?
In the standard conversion they match through G, but many brands diverge after DD — for example, US DDD is often labeled E in UK sizing. Check each brand's chart in larger cups.
How do European sizes fit into this?
EU sizing is a separate system that numbers bands in centimeters (a 34-inch band is about EU 75) and uses its own cup sequence. It is not interchangeable with either US or UK labels.
If I am a 36C in the US, what am I in the UK?
A 36C. Below DD, US and UK cups use the same letters, so no conversion is needed for the most common sizes.