UK to US Dress Size Conversion
| UK | US |
|---|---|
| 4 | 0 |
| 6 | 2 |
| 8 | 4 |
| 10 | 6 |
| 12 | 8 |
| 14 | 10 |
| 16 | 12 |
| 18 | 14 |
| 20 | 16 |
Sizing conventions vary by brand and by cut — this table shows the standard published conversion. Always check the garment's own size chart when one is available. See how these tables are compiled.
Why the four-number rule is a moving target
UK and US women's dress sizes both run on an even-numbered scale, four numbers apart on the standard chart — a UK 10 converts to a US 6 — but that gap has been pulled apart over recent decades by 'vanity sizing', the gradual practice of labeling the same actual measurements with a smaller number to make the size more flattering to the buyer. US sizing has generally drifted this way faster than UK sizing has, so the four-number rule is closer to a historical average than a fixed constant true of every brand today.
A practical consequence: two US dresses labeled the same converted size from a fast-fashion brand and a more traditional department-store brand can differ noticeably in actual measurements, because they've drifted from the historical baseline at different rates — the UK size you're converting from is a more stable reference point than the US number you're converting to.
Pattern blocks add a second layer of difference
Independent of the size-number drift, US and UK dressmaking traditions have historically drafted patterns around somewhat different body-shape assumptions, so a UK size correctly converted to a US number can still fit differently through the waist and bust in a fitted dress than a US-drafted dress would, even when the size label matches. Loose, unstructured silhouettes are far more forgiving of this than fitted ones.
The safer check for an unfamiliar US brand
For a US brand you haven't ordered from before, the four-number offset is a place to start, not a place to stop — brands that have drifted furthest from the historical baseline are exactly the ones where a bust/waist/hip cross-check matters most.
Formal wear runs its own scale on both sides
UK bridal and occasion-wear sizing is also commonly tighter-running than everyday UK ready-to-wear, similar to the US pattern, which means converting a UK formal size using the everyday four-number offset can undersize the US result. Formal and bridal retailers on both sides of the Atlantic tend to publish their own dedicated chart precisely because their sizing doesn't track their everyday clothing lines.
UK petite and tall ranges, much like their US counterparts, adjust vertical proportions rather than girth, so converting the size number alone doesn't tell a US shopper whether they should also be looking at a petite or tall version of the equivalent US style — that's a separate decision from the size-number conversion itself.
Frequently asked questions
Is UK 10 always a US 6?
It's the standard chart pairing, but vanity sizing has drifted the two scales apart unevenly over recent decades, more so in the US than the UK, so some American brands now require converting to a smaller US number than the historical four-number rule suggests.
Why do two US dresses in my converted size fit so differently?
Different US brands have drifted from the historical sizing baseline at different rates, so a fast-fashion label and a traditional department-store label can label noticeably different actual measurements with the identical converted number.
Does a fitted UK dress convert to US sizing as reliably as a loose one?
Less reliably — fitted and structured styles depend more on the underlying pattern block, which differs somewhat between US and UK dressmaking traditions, while loose, flowing silhouettes are more forgiving of that difference.
Is my UK size a more stable reference point than my US size?
Generally yes for this purpose — UK sizing has drifted less aggressively than US sizing over recent decades, so converting from a known UK size is a steadier starting point than assuming a fixed US number applies everywhere.
Should I use the everyday conversion for a UK bridesmaid dress?
No — check the specific bridal or occasion-wear retailer's own chart, since formal categories commonly run a tighter, separately calibrated scale from that brand's everyday clothing.
Does the UK-to-US conversion tell me if I need a petite or tall size?
No — that's a separate, height-related decision. The size-number conversion addresses girth only; petite and tall ranges adjust vertical proportions independently on both sides.