Approximate women's clothing size conversion between US, UK and EU.
Clothing sizes differ between countries by a predictable offset in some cases and not at all in others. Roughly, a UK women's size is two numbers above the equivalent US size, and European sizes run about 28 higher than UK — a UK 12 is broadly a US 8 and an EU 40. Men's shirts are more rational, since European sizing usually states the collar measurement in centimetres, which is an actual dimension rather than an arbitrary label.
The bigger problem is that sizes are not standardised even within a country. Two garments labelled the same from different brands can differ by several centimetres, and there is no enforced definition of what any size means — a genuine source of frustration rather than an urban myth. Vanity sizing, where brands relabel larger garments with smaller numbers, has widened the drift over decades. The practical answer is to ignore the label and use the brand's own measurement chart against your actual body measurements: chest or bust, waist, hips, and inside leg. A conversion between number systems is a starting point, never a guarantee of fit.
Roughly, a UK size is two numbers above the US equivalent, and EU sizes run about 28 above UK. So a UK 12 is approximately a US 8 and an EU 40. Treat this as an approximation rather than a rule.
Because clothing sizes are not standardised. Each brand sets its own measurements, and there is no enforced definition, so identically labelled garments can differ by several centimetres.
The practice of labelling larger garments with smaller numbers. It has shifted sizing gradually over decades, which is why older garments often run noticeably smaller than current ones with the same label.
Measure yourself and compare against the specific brand’s size chart rather than relying on a number. Chest or bust, waist, hips and inside leg cover most garments, and charts are generally published per brand.