What are the dimensions of a LEGO brick? What are the real world dimensions of bricks? (starting with 1x1 brick) Plates? Studs? Does LEGO think of this in metric or imperial units or something else?
This image shows the dimensions in LEGO Units. 1 Lego Unit is 1.6mm (the thickness of the plastic wall).  In those units the stud's diameter is 3 (= 4.8mm).