Your room size plus the number of people you want to seat will dictate your table size. For the table placement in the room you usually want between 42-48″ between your table and the walls. If there is furniture in the dining space, begin your 42-48″ measurement from the edge of the furniture instead of the wall. You want to allow for about 24” of eating space per person so you aren’t bumping elbows. Many customers mention taping out the table size on the floor to get a feel for it in the space.
Please keep in mind that these are just general suggestions.