I wear a size 11 mens in Nikes, New Balance, Rockports, Toms, Crocs, Reef Sandals so when I saw I needed to buy one size bigger I did. The first time I put the boots on I realize that the boots are one size too big and slide around on my feet.  Im really disappointed that I now have a size 12 boot for my size 12 foot.  A simple walk around the office shows that I will not be able to wear these, even with the thickest of socks.  The slippage is pretty bad, and I know I will wear holes in my feet.  The calf isn't contricting at all.  I've read that on other reviews too.  Buy your size for your current foot, and you shouldn't have any issues.