An Italian 42 Is Not an Italian 42
Designer resale listings quote whatever the label says, and the label says whatever the house that made it uses. A French 38, an Italian 42, a UK 12 — all plausibly the same dress, and all equally plausibly not.
The size converter holds a chart per category, and the interesting part is what happens when you compare the charts to each other.
Women's apparel, across every system
| US | UK | EU | IT | FR |
|---|---|---|---|---|
| 2 | 6 | 34 | 38 | 34 |
| 4 | 8 | 36 | 40 | 36 |
| 6 | 10 | 38 | 42 | 38 |
| 8 | 12 | 40 | 44 | 40 |
| 10 | 14 | 42 | 46 | 42 |
| 12 | 16 | 44 | 48 | 44 |
A women's US 6 is a UK 10, an EU 38, an Italian 42 and a French 38. Two of those numbers are the same and three are different, which is the entire problem in one row.
The trap
An Italian 42 in womenswear is a US 6 — a small size. An Italian 50 in menswear is a US 40 — a mid-size jacket. Same number, entirely different garment.
Italian sizing runs 4 numbers above EU for womenswear and matches EU exactly for menswear, so the two systems collide at values that look identical and are not. A listing that says "IT 42" without saying what it is has told you very little.
Shoes are worse
| US size | Women's chart | Men's chart |
|---|---|---|
| US 6 | UK 4 / EU 36 | off the chart |
| US 8 | UK 6 / EU 38 | UK 7 / EU 41 |
| US 10 | UK 8 / EU 40 | UK 9 / EU 43 |
A US 8 is EU 38 for a woman and EU 41 for a man — 3 numbers apart, from the same printed US number.
The underlying rules are simple and different: women's EU is roughly US + 30, men's EU is roughly US + 33. Nobody misreads their own chart; people misread the other one.
What to do with a listing
Establish which chart first. Not the number — the category. A unisex or ambiguous listing is a question to ask before anything else.
Convert through the tool, not in your head. The arithmetic is easy and the charts are the thing that catches people, which is precisely when a lookup beats a calculation.
Then ignore the conversion and ask for measurements. This is the real advice. Bust, waist, hip, shoulder, sleeve, and for shoes the insole length in centimetres.
Why measurements beat conversions
The converter's own documentation is explicit: sizing is approximate, brands cut differently, and a conversion is a guide rather than a guarantee of fit. That is not modesty — it is the single most important fact about designer sizing.
A French house's 38 and an American brand's 6 are nominally equivalent and can differ by several centimetres in the bust. Older pieces are cut smaller than new ones in most houses. A tailored jacket and a knit in the same nominal size are not the same garment at all.
Measurements are physical and comparable. Sizes are a label's opinion.
When the converter returns nothing
It returns nothing for any value not on the chart, rather than interpolating — half sizes, odd sizes, and the extremes at either end.
That is deliberate and correct. A converter that invented an answer for a US 7.5 shoe would be producing a number no manufacturer uses, and the honest response to an off-chart size is to ask for the measurement.
The resale-specific problems
Vintage runs small. A 1990s piece in a nominal size is typically a size or more tighter than the same label today, and no conversion chart knows what year the item is from.
Labels get cut out. Common in resale, and it makes measurements the only information there is.
Alterations are invisible. A taken-in dress carries its original label and its new measurements, and only one of the two is true.
Returns are limited. Many resale purchases are final sale, which is what turns a sizing error from an inconvenience into a purchase with a cost-per-wear of infinity.
The habit worth building
Measure one garment you already own and love — the one that fits best in each category — and keep those numbers in your phone. Every future listing becomes a comparison against a garment that demonstrably fits you.
It removes the conversion problem entirely, it works across every brand and era, and it is the only method that survives a missing label.
The systems, and what each is really counting
EU sizes are derived from body measurements in centimetres, which is why they run in even numbers two apart.
UK and US are arbitrary scales offset from each other by a fixed amount within a category — hence the constant gap of 4 in the women's apparel table.
IT and FR are national systems that happen to be printed on a large share of luxury labels, and the Italian one is the one that collides most often with EU.
None of them is a measurement of the garment. All of them are a label's claim about who it is for.
A short procedure for a listing
One: identify the category — women's or men's, apparel or shoes.
Two: convert with the tool, and note that it returns nothing rather than guessing for off-chart values.
Three: ask for measurements anyway, and compare them to a garment you own.
Four: ask about alterations, because a taken-in garment carries a label that is no longer true.
Why this matters more in resale than in a shop
In a shop you try it on. In resale you are buying a label's opinion, often from a different decade, frequently final sale, and increasingly with the label cut out.
The conversion chart narrows the field; measurements decide it. Anyone who buys designer resale regularly ends up working entirely from measurements, and the conversion becomes a first filter rather than an answer.
The one habit
Measure your best-fitting garment in each category once. After that every listing is a comparison against something that demonstrably fits, and no conversion chart is needed at all.