US vs UK Bra Sizes: Where They Match and Where They Split

If you've ever ordered from a British brand and found the cups gaping, or bought a US bra in your "usual" letter and ended up spilling over the top, the problem probably wasn't your measurements. It was the label. Both countries measure bras exactly the same way. They just name the bigger cups differently, and nothing on the tag tells you which naming scheme it follows.

What the two systems agree on

Underneath the labels, US and UK sizing use the same recipe:

• The band is your ribcage measurement in inches, usually an even number: 30, 32, 34, 36 and so on. A 34 band is a 34 in both countries.
• The cup comes from the gap between your bust and band measurements. Every extra inch of difference moves you up one cup step.

So far, so simple. One inch is an A, two inches a B, three a C, four a D and five a DD — in both countries. The disagreement starts at six inches, and it's purely about what to call each step from there on.

Side by side

The full US to UK cup conversion chart

Each row is one inch more of bust-to-band difference. Rows in green are identical in both countries; the highlighted rows are where the labels split.

US brands are less consistent than UK brands above DD. The most common US pattern is shown; always check a brand's own chart when it uses E or F.

Notice the pattern: the UK slots in doubled letters (FF, GG, HH, JJ) as steps of their own, while the US uses DDD once and then carries on through single letters. That's why the gap between the two labels grows as you go up. At seven inches it's one letter apart (G vs F); by fourteen inches the US has reached N while the UK is still on J.

The tricky letters

E and F: the two letters that cause most mistakes

Most conversion mix-ups happen around E and F, because both countries use these letters — just for different steps.

• A UK E is six inches of difference. In the US, that same step is usually called DDD.
• A US E is a moving target. Some US brands print E as an alternative name for DD (five inches); others use it for DDD (six inches). It almost never means the same as a UK E.
• A UK F is seven inches. Most US brands call that a G. A US F, when it's used at all, is usually the six-inch step — one full cup smaller than a UK F.

The practical rule: whenever you see E or F on a label, don't trust the letter on its own. Find out which country's system the brand follows, or look up the inch difference on the brand's size chart.

Worked conversions

Below DD there's nothing to convert: a US 32C is a UK 32C, and a US 36DD is a UK 36DD.

Reading a label

How to tell which system a bra is using

Shops rarely say "US sizing" or "UK sizing" on the tag. These clues usually give it away:

If you shop in India, most local retailers follow the UK pattern (inch bands with UK cup letters), so convert US sizes exactly as you would for the UK.

Before you order across the Atlantic

• Start from your measurements, not an old label. Run them through the bra size calculator and note the inch difference, not just the letter.
• Convert the cup, keep the band. If a UK 34FF fits you, look for a US 34H — don't change the 34.
• Keep a sister size in reserve. If the converted size runs firm in the band, a sister size one band up and one cup down keeps the same volume.
• Do the fit check anyway. Conversion fixes the label, not the cut. Brands shape cups differently, so check the band, gore and wires before removing tags.