I was trying to buy a Patagonia jacket on closeout at the local Patagonia store, size chart says I am a small. Mainly because I have a store credit due to a defective jacket. I try on a small; I have a 38 inch chest, 29 inch waist, 33.5 inch arm length, 15 inch neck size; according to their size chart, there should be no issues. Well, the jackets, in this case the Pow Slayer, Powder Bowl, and Primo, are all swallowing me! A friend with me, who is about 6 foot and 190lbs, tries it on; fits him perfectly. "Wow, I haven't been a small since Junior High!" he says. Unfortunately, I probably need to buy an XS, but since the local store doesn't stock it, I am probably out of luck. I am not exactly the smallest guy either: 5 foot 9, 158lbs. Trim, sure, but big for a bike racer. The "small" would fit me if I were 3 inches taller and 30 lbs heavier.
What frustrates me is their inaccurate sizing. There is a huge difference between "relaxed" fit and "Tom Hanks at the end of "BIG" baggy". This jacket is the latter. I don't want to look like some park rat kid, and their alpine jackets, although sweet, didn't really have the on-snow features I was looking for in a ski jacket, as I already have one of their alpine softshells (which, in small, fits perfectly). It seems like they are going off on this tangent, making stuff in sizes and models that stray from their core base and may harm their reputation. Did they get purchased by a hedge fund or something? Or are they trying to sell to the Park crowd by turning off loyal customers? Most Patagonia buyers aren't people who hang out in the park: they tend to be climbers/outdoor people like me.
Anyways, just a warning. If you have an athletic build, you will probably have to size down, or look at something else.
FWIW, their alpine lineup fits true to size, even the ones I tried on at the store.