Try a few on.
http://www.onlineconversion.com/clothing_womens.htm <<try that website. Or just Google a size converter there are several you can look through them.
its size 38
Its size 46
That would be size 44 in Italian pants
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The American Size for American Size 33 pants is American Size 33.
That would be size 42 in Italian sizes
The American size for a British size 30 pants is a size 28. These sizes correspond to a waist of 127 cm and bottom hips of 149 cm.
its size 10
size 8
It would be a 43.
size 12
it's a size 26 or 28