Eli5: Why are clothing brand sizes different from each other even though they all use the same scale? (i.e. xs-xl)

Question

If I know that I’m a size L at one clothing store why is it when I go to a different clothing store I’m forced to move to a XXL or M to get a decent fitting option?

In: 14

Answer 1

Brands typically assign their size labels based on their perceived customer base. So one brand might have an overall thin customer base so their XS will be smaller than an XS from a brand with bigger customers on average