Sizing is completely confusing to me too! And it's not just in numbers, it's the whole small, medium, large thing too!
I have an old pair of capris from two summers ago that are a 16 petite and they are just a tiny bit loose. To compare, I bought a new pair of size 13 regular and they are slightly too snug. I have noticed I can be as small as a 12 petite and up to a 15 regular, depending on cut and style.
Same goes for t-shirts. I can wear anything from a SMALL to an X-LARGE. Seriously? All depending on where I've bought my shirt!
They're up in your face, they don't think you belong
Man, you got it, you got it goin' on
What breaks the weak just makes you strong
You got game, baby bring it on, bring it on