UK, US, EU and Italian Sizes Compared
A UK 12, a US 8, an EU 40 and an Italian 42 are meant to be the same garment. Knowing the offsets makes shopping across markets far less of a lottery.
The offsets are constant
Across the standard women's range the relationships hold steady:
- UK = US + 4
- EU = US + 32
- Italian numeric = EU + 2
So a US 4 is a UK 8, an EU 36 and an Italian 38. A US 12 is a UK 16, an EU 44 and an Italian 46. The size converter holds the whole table, from US 0 (UK 4, EU 32, IT 34) to US 20 (UK 24, EU 52, IT 54).
Why Italian sizing runs larger again
The Italian numeric convention sits about two sizes above the EU/French numbering for the same measurements, which is why a label reading 42 can be an EU 40. It is a labelling convention rather than a difference in the garment.
This catches people buying Italian brands online, where the number looks alarming and the fit is ordinary.
The offsets are the easy part
Here is the important caveat, and it is a large one: these conversions describe the nominal size systems, not what any particular brand actually cuts. Two garments labelled UK 12 from different brands can differ by several centimetres.
Vanity sizing has also moved the reference over the decades, so a vintage size is not a modern one. The conversion tells you which number to look for on the rail; it does not tell you whether it will fit.
Always check the brand's own chart
Every reputable retailer publishes measurements — bust, waist, hip in centimetres or inches — against its size labels. That table is authoritative for that brand and the conversion is not.
The reliable process is to know your own measurements, find them on the brand's chart, and ignore the number entirely. It takes a minute and it is the single most effective thing you can do to reduce returns.
Measure yourself, not a garment you own
Measuring a favourite item and matching it works only if the new garment has the same cut and fabric. A woven blouse and a jersey top with identical flat measurements fit completely differently.
Your own bust, waist and hip — the same three the shape calculator uses — travel between brands in a way a label never does.
Different garments, different rules
The conversion covers standard apparel sizing. Shoes, denim and lingerie each run on their own systems: denim is usually a waist measurement in inches, bras combine a band measurement with a cup letter, and shoe sizing has its own set of regional offsets.
Do not carry an apparel conversion into those categories.
Order two sizes when it matters
For anything structured — tailoring, coats, anything fitted at the waist — ordering the size the chart says and the one above is usually cheaper than a second round of shipping. Fit varies most in exactly the garments where fit matters most.
For jersey and knitwear, one size and a bit of tolerance is normally fine.
The four systems, side by side
| US | UK | EU | Italian |
|---|---|---|---|
| 0 | 4 | 32 | 34 |
| 2 | 6 | 34 | 36 |
| 4 | 8 | 36 | 38 |
| 6 | 10 | 38 | 40 |
| 8 | 12 | 40 | 42 |
| 10 | 14 | 42 | 44 |
| 12 | 16 | 44 | 46 |
A US 8 is a UK 12, an EU 40 and an Italian 42. Four numbers, one garment, and only one of them appears on the label you are looking at.
The offsets, once you see them
UK runs 4 above US. EU runs 32 above US. Italian runs 2 above EU — which is the one that catches people, because an Italian 42 and an EU 42 are different garments and the label rarely says which convention it is using.
The offsets are constant across the range, so one conversion learned is every conversion learned. What is not constant is anything else about fit.
Why the conversion is a starting point
Sizing is a label's opinion, not a measurement. Two houses quoting the same EU 40 can differ by several centimetres in the bust, older pieces are cut smaller than new ones in most houses, and a tailored jacket and a knit in the same nominal size are not the same garment at all.
So the conversion narrows the field and measurements decide it. Bust, waist, hip, shoulder and sleeve for tops; waist, hip and inseam for bottoms.
The habit that removes the problem
Measure the garment you already own and love — the best-fitting one in each category — and keep those numbers in your phone. Every future purchase becomes a comparison against something that demonstrably fits you, in any system, from any decade.
It works when the label has been cut out, when the piece has been altered, and when the brand's own chart is optimistic. None of those is unusual, and all three defeat a conversion table.
Vanity sizing, briefly
The same nominal size has grown over decades, so a vintage US 8 is smaller than a current one — sometimes by two sizes. Nothing in the converter knows the year a garment was made.
Which is another argument for measurements: they are physical and comparable, and they do not drift with fashion or with a brand's opinion of how its customers would like to feel.
Buying across systems without returns
Ask for the garment's flat measurements — chest across, length, sleeve — and compare them to something you own. Most sellers will provide them, and a seller who will not has told you something useful.
For anything final-sale, that comparison is the entire protection you have, and it works where a size chart does not: a garment measured is a fact, and a size quoted is a claim.
The one to memorise
Your own row. US 8 / UK 12 / EU 40 / IT 42 is one line, and having it means never converting anything again — only checking measurements when the fit matters.