There is no hard-and-fast rule about the height of lighting hung over furniture. The light should look good in the room and be functional. When hanging a light above a table, thinks about what activity will usually take place at the table. The height of the fixture must allow for enough head space, so that it does not interfere with normal activity and, at the same time, offers the right amount of illumination for the task at hand. A good rule of thumb is to initially hang the light fixture between 30 to 36 inches above the table, and adjust it until you get the proper illumination.
Tables are used for a variety of functions, some as office space and others solely for dining. Families with children often find that the table is a gathering spot for the little ones to do their crafts. If the table does double duty as a work area, allow at least 36 inches between the top of the table and the bottom of the light fixture, so that the hanging light is not in the way but still gives the proper illumination for the projects at hand.
Lighting fixtures and chandeliers over a table in a formal setting are most often hung at a height that enhances the decor of the room. If the fixture is hung too low, it can detract from the overall attractiveness of the table setting, especially if a large centerpiece usually adorns the table. A table in a formal room is not usually used as a work area, but for entertaining and dining. Appearance, not illumination, is the key. As well, the size of the lighting fixture will influence the height from which it should be hung.
Ceiling height differs from home to home. If you are installing a light fixture in a room with a high ceiling, the usual guideline of hanging it 30 to 36 inches above the table surface might not apply. Consider a minimum of 36 inches, and adjust the fixture higher until you find the proper height.