I went up a full size based on the centimetre numbers in the size chart. Don't be fooled! The JP size numbers correspond to the actual CM of the boot size. For example, a size 10 is 28cm, not 27. I am happy with my size 10s and don't feel the need to have them half a size bigger. These are comfortable, stylish boots with a very solid sole. Haven't hiked with a big pack yet, so the true test awaits. Keen has earned my trust in the past and I would expect these boots to hold up.