After reading previous reviews I was still confused as what size to get. Reviews said they were too big for their usual size, yet no one said what size their usual size actually was, to compare. So, I’m a UK12 (used to be an 8 but not sure what happened!) & decided to buy a size 12 hoodie. It arrived & the size on the tag said M. It fitted nicely, roomy but not baggy. My chest is 36B & there was still room for a bit more boobage, which I don’t have! Don’t think I’d get under armour on underneath, so I’d probably want to size up if I was going to do that. It feels snug & warm, though not particularly thick, yet definitely not thin & cheap. I wore it while driving my open top kit car & even though it was a bit chilly, the hoodie took the edge off the cold. This will probably be my new favourite hoodie.