I'm 5'1" and 125 lbs., and I ordered a small. The arms are 2 inches too long, which I expected given my height, but the cuff is exactly 2 inches and looks fine turned up. I am wearing the sweater buttoned to the side. Buttoned traditionally, it's a bit boxy, but I never intended to wear it that way.
I could have gone with an XS, but I wanted more of a jacket sweater for fall. It is not scratchy for me as one review said. I find it soft. I will be wearing this a lot, I can already tell.

Cut is very cute but the fabric is SO itchy!

Great to wear—compliments coming as soon as step out door

Love this sweater…great quality…thick, very soft…color and shape just like the pics on line…can be worn like a traditional cardigan or to the side which is a fun modern look. Well priced and great quality…highly recommend…true to size

Gorgeous sweater - love the asymmetric option!