How the conversion works
Women's numeric sizes convert by fixed offsets from the US size: UK and Australia are US + 4, Germany and the Netherlands US + 30, France US + 32 and Italy US + 36. So a US 8 is a UK 12, DE 38, FR 40 and IT 44.
Men's tops and jackets are based on chest measurement. US, UK, Canadian and Australian sizes use chest in inches. European sizes add 10, so a 40-inch chest is an EU 50.
Why this is only a starting point
There is no enforced international standard. Brands grade and label differently, and vanity sizing shifts labels over time. If you are building a range for several countries, label garments with measurements and publish your own size chart. The size chart generator helps you make one.
Common questions
Is UK size the same as Australian size?
For women's numeric sizes they are generally labelled the same, though individual brands vary.
What should I print on labels for several markets?
Many brands print two or three systems on one label, such as US, UK and EU, alongside a letter size.