How do you convert US, UK and EU sizes?

What does a size conversion table actually tell you?

It helps to be precise about what these tables actually claim, because people tend to read more into them than is there.

A conversion table describes the relationship between national numbering conventions. It says that when the British convention calls something a 10, the American convention has usually called the same thing a 6, and the German and French convention has usually called it a 38.

Notice what is missing from that. It says nothing about any particular brand, because a brand grades from whichever fit block it chose and it does that regardless of which country it happens to be selling into. A conversion describes the conventions. Your garment was made by a company.

What is the UK to US to EU size conversion?

Here it is for womenswear, as it is commonly published. Use it to find the right row on a chart, then read the centimetres in that row.

Three arithmetic rules sit under that table and are worth carrying in your head instead of the whole thing. US is usually the UK number minus four. The EU number, meaning the German and French scale, is usually the UK number plus twenty-eight. Italian is usually the UK number plus thirty-two, which is why an Italian label often looks two numbers larger than an EU one for the same garment.

Australian womenswear tracks the UK closely enough to use the same number as a starting point.

When does a size conversion put you a size out?

A straight conversion will put you a full size out in three specific situations. All three are common and none of them are flagged on the product page.

A brand grading from a foreign base. Plenty of labels sell internationally while building their patterns onto a block from somewhere else, and then print whichever country's numbers suit the market they are shipping to. The number has been converted and the garment has not, so the conversion and the reality point in different directions.

A brand whose own convention is already offset. Some labels sit deliberately small or deliberately generous against their home market. Convert into that brand's scale and you inherit the offset on top of the conversion, and the two can compound.

The ends of the range. Conversions are steadiest in the middle sizes, where the conventions were originally lined up against each other. At the top and bottom the national scales drift apart, and a conversion that was reliable at a UK 12 can be a full size out at a UK 20.

What does one UK 12 become at three different brands?

Put a UK 12 through the standard conversion at three brands that each handle it differently, and the table's limits become concrete rather than abstract.

A standard-block brand is the case the conversion table was built for, and it is genuinely reliable there. The other two rows are not failures of the table. They are brands that never matched what the table assumes in the first place, and the only way to tell which kind you are ordering from is to check one chart against the table once and remember the result.

What size is a medium?

Small, medium and large are not a shorthand for a numbered size. They are their own scale, and a much coarser one.

A letter usually spans two numbered sizes, sometimes three, and where that span sits is entirely up to the brand. One label's medium starts where another's begins to end. There is no arithmetic rule available because there is nothing consistent to build one on.

So for a garment sold in letters, the chart carries more weight rather than less. Where a letter-sized item publishes no measurements at all, you are being asked to guess, and the only sensible response is to check the returns policy before ordering.

Why is menswear sizing easier to convert?

Worth knowing because it explains why this feels like a womenswear issue.

A large amount of menswear is labelled in actual measurements. A shirt sold by neck size, a trouser sold by waist and inside leg, a suit sold by chest measurement: all of those are giving you a number in centimetres or inches, and a number needs no conversion.

The catch is that those measurements are still body measurements with the brand's own ease added on top, so two shirts marked with the same neck size can fit differently through the body. Where menswear uses letters or a jacket number instead, it inherits every problem described above.

How do you convert shoe sizes between countries?

Clothing conversions shift by a roughly constant offset. Shoe conversions do not, because UK, US and EU shoe scales are built on different unit lengths in the first place, so the gap between them changes as the foot gets bigger.

As a starting point, a UK size is commonly one number below the equivalent US women's size and about half a size below US men's. EU sizing runs on its own scale again, roughly the UK number plus thirty-three. None of those offsets are exact at every size, which is the opposite of the clothing table above, where the offset barely moves across the whole range.

The reliable fix is different for shoes too. A brand's printed insole length in centimetres, when it publishes one, is worth more than any of the three size numbers, because a foot is a length in a way a torso is not. Where no insole length is given, the size the retailer's own site recommends for a known reference shoe beats a generic conversion chart every time.

How does children's sizing work?

A children's size is not a smaller version of the adult scale, and treating it as one is a common way to order two sizes wrong at once.

UK and US children's clothing sizing is commonly given by age or by height in centimetres, and the two do not always agree for a particular child. A label reading "7-8 years" is a manufacturer's estimate built around an average height for that age, and plenty of children sit outside it in either direction.

Where a children's chart gives height alongside the age band, use the height. It is the actual measurement, and the age is the guess sitting next to it. Once a child is tall enough for adult-cut clothing, usually somewhere around age twelve to fourteen depending on the brand, the ordinary womenswear or menswear conversion above starts to apply again.

Why does Asian sizing run smaller?

Several Asian markets grade from a smaller base than European and North American ones, so the same label covers a smaller body. This is a difference in the underlying block rather than a numbering convention, which means no conversion rule fixes it cleanly.

Retailers selling internationally handle this two ways. Some publish a converted chart aimed at the market they are shipping to. Others publish their domestic chart and leave the conversion to you. The product page rarely says which it has done.

The reliable move is to ignore every label and read the centimetres. If a chart lists a bust measurement, it does not matter what scale the number beside it belongs to.

What does converting a UK 12 to an Italian size look like?

You normally buy a UK 12 and you have found a dress on an Italian retailer's site. The size options are 40, 42, 44 and 46.

Convert first to find the row. UK 12 plus thirty-two puts you at IT 44, so that is where to start looking.

Now check the chart rather than ordering. The chart lists bust, waist and hip in centimetres. Your bust is 94, and the chart puts 94 at IT 42. The conversion said 44 and the chart says 42, which is exactly the disagreement this chapter is about.

The chart wins. It was written by the people who made the dress, and the conversion was written about a country. Order the 42, and note in your own brand list that this label runs one size generous against the Italian convention, so the next purchase takes ten seconds.

Which three rules always hold?

The conversions are worth knowing and they do a specific, limited job. These are the rules that hold when everything above is competing.

1. Convert to find the row, never to place the order. The table narrows nine options down to one or two. The chart decides between them.
2. Centimetres beat every label. A measurement in a chart means the same thing in every country. A number on a label means whatever the brand decided.
3. Write down what you learn. One line per brand, kept with your own measurements, removes the conversion question from every repeat purchase from that shop.