I normally wear a 12 or 14, and I wear a large in Ibex. (I think I just bought the last Large Carrie hoody from High Country, and it was in Thistle, too!) I have very long arms, so I just tend to buy large enough to fit my arms. But Ibex Large not only fits my arms, it also fits my torso!
Luuuuuuuuv Ibex!