I am going to have to do this again, since I lost my list - but the same thing is true for me with shoes. I once went on a shoe-trying-on expedition to try and determine my size in various brands. I take a size 7, 7.5, 8 and even a size 9 in a recent pair of flat booties. Meanwhile, even if I know I take 7.5 in Clark's shoes, I ordered some nice sandals last summer (loved them soooo much), but they fell off my feet at the heels. I was so disappointed. I used to have an actual list in my wallet - yes, on paper - of what brands fit me in shoes and in what size. I have trouble with shoes for some reason - they like to fall off my ankles and sometimes I can't keep a shoe on at all, no matter what the size.
Same is true for clothes too, but I don't have a clear/consistent idea of what size I am in a particular brand or store - it sometimes depends on the item and how I want the item to fit. For instance, the SA at Gap was suggesting a size 8 in their Really Skinny pants, and for a 'skinny fit' I would have chosen a size 10 - but I actually ended up buying a size 12 because I didn't want them to be as body-con as the makers intended them to be. I was looking for slim, but not super-close-fitting pants.
I've also bought petite tops to wear with skirts (untucked). I am not petite at 5', 6" tall as far as I can tell. That said,a petite-sized top/blouse or even jacket can sometimes work well for me as a top to wear specifically with skirts.
Agree with you though, that sizing is all over the map. Things don't make much sense to me at all.
