I would say for the most part this product is true to size. This coat has proven to be very satisfactory for the 30 degree weather we've been having this fall, but it definitely won't suffice beyond mid November. The coat is good quality and overall worth the money.
I am a 5'4" and about 117lbs, I order a size 4 and it fit perfect. Very stylish, although I had to sew a button back onto the sleeve that came loose. The pockets are nice and deep enough to keep my cell phone in. I would recommend this purchase.