It depends on the shoe that you have from MORJAS.
If you have The Oxford, The Derby, The Double Monkstrap, The Single Monkstrap or any of our boots: go down half a size. In other words, if you wear UK10 in the above mentioned shoes we recommend going for UK9.5 in our loafers.
If you have our sneakers: go down half a size. If you wear UK10 in our sneakers, select UK9.5 in our loafers.