I normally wear a 9.5 so I ordered the size 10. I do have to wear a thicker sock to make up the space, but with the thicker sock the boot is really comfortable. I'd say my calves size are normal to a little thicker, and the calf of the boot fits perfect. It's not too tight, but it's also not too loose. There is plenty of room in the boot with a thicker sock and a layer of leggings or skinny jeans.