How UK and US bra sizes relate
UK and US bra sizes start from the same place. Both measure the band in inches, and both add one cup letter for each inch of difference between bust and band. So for most everyday sizes, there is nothing to convert. A UK 32B is a US 32B. A UK 36D is a US 36D.
The two systems only part ways in how they name the larger cups. Once you understand that one difference, the converter above is just a quick check.
Bands: no change
UK and US bands use the same numbers: 28, 30, 32, 34, 36 and up. The converter leaves the band as it is.
What can differ is how a brand cuts its band. A firm British label and a softer American label can both say 34 and still feel different. That is a brand difference, not a country difference, and a sister size is the usual fix.
Cups: same up to DD, then different names
Up to DD, the letters match exactly: AA, A, B, C, D, DD.
After DD, the UK continues with E, F, FF, G, GG, H, HH. US brands more often continue with DDD, then G, H, I, J. Put side by side, one step at a time:
- UK E is US DDD
- UK F is US G
- UK FF is US H
- UK G is US I
- UK GG is US J
Each line is the same cup volume with a different label. The UK counts its double letters as full steps, so it uses fewer different letters to cover the same range.
US brands do not all follow one pattern above DDD. Some use DDDD, and some use F where others use G. The converter follows the most common pattern. For any cup above DDD, compare with the brand’s own size chart before you buy.
Worked examples
- UK 34E converts to US 34DDD.
- UK 32F converts to US 32G.
- UK 36FF converts to US 36H.
- UK 30GG converts to US 30J.
In every case the band stays put and only the letter changes.
Where people go wrong
The most common mistake is reading a UK letter as if it were a US letter. A UK F is a US G. Some US brands use F as another name for DDD, so ordering a US F for someone who wears a UK F can give a cup one size too small.
The second mistake is changing the band. There is no need. If you know the UK band, you know the US band.
When you are buying from the other country
Whether the brand is British and you shop in the US, or the other way round, the routine is the same:
- Start from a size that fits well, ideally from a bra she wears often.
- Convert the cup only.
- Check the brand’s chart if the cup is above DD.
- Keep the tags on until the fit is confirmed.
If you have no size to start from, measure first with the how to measure bra size guide. If you are buying for a partner and only know the size from a tag, the from her bra tag guide explains how to read it. For other country pairs, use the main bra size conversion page.
Don’t know the UK size yet? The UK bra size calculator measures in centimetres or inches and gives UK cup letters directly.
Sources & method: sizing rules follow the standard band-and-cup system used by UK, US, AU and EU brands, checked against fitting guides from specialist retailers and fitting communities. How we work.