Vans is a US brand, so their default sizing is in US. Vans run true to size and are available in unisex sizing.
Please note: Vans do not offer full women's sizes, only half sizes. However, if choosing from the women's sizing we recommend sizing up (e.g. grab a women's US 9.5 if you're usually a US 9). You can view the Vans size chart here.
In this video below, the US men's 6 is selected, which is equivalent to a US women's 7.5 and an EU 38.